It's anachronistic. In that case all groups who hold Jesus as important in the divine economy are Christians (Gnostics, Manicheans, etc).
Dye do the same mistake in Q 19. He considers that Q 19-1-33 is Christian. He's wrong. Christianity (Chalcedonians, Monophysites, Nestorians) has very clear dogmas: Jesus is the Son of God : as such he is God. in Q 19-1-33 Jesus is a prophet.
Dye will say: "I never said that" . The issue is that he insists more on what brings closer the passage to Christianity what separates it from. Now, this is precisely the nature of Jesus which separates (among other things) what says the Quran from the Christians dogmas.
Q 19:1-63*[ less 34-40] is a text which can be described as almost Christian, or even as Christian: in fact, it is unclear how it could be possible to be closer to Christianity, except by simply asserting some specific Christian dogmas – something the text does not do, of course. All the details of the text have their origins in written, liturgical or popular Christian traditions (more on this
below), and can be acknowledged by Christians. It is therefore appropriate to speak here of a “text of convergence”.13 Moreover, with its stanzas, refrain, and alternation of narration and dialogues, this text looks like a well-known literary genre in Syriac religious literature: the soghitha, a dialogue poem involving Biblical or prophetic characters [...]
Let us look indeed at the profile of the author of Q 19:1-63*.64 [ less 34-40]
1) He is familiar with Luke 1 and related traditions (compare Luke 1:13 and Q 19:3-4; Luke
1:13-22 and Q 19:7-11;65 Luke 1:28-38 and Q 19:17-21).
2) He has an intimate knowledge of the traditions related to the Kathisma church –
including the Protoevangelium of James and the palm miracle – and he presupposes the
connection between these independent traditions. He knows, one way or the other, the
Lection of Jeremiah, a text which was clearly not widespread outside the Hagiopolite
communities.
3) He is familiar with other aspects of the Jerusalem Marian liturgy and with the Dormition
narratives. In fact, relying on the network of subtexts constituted by the Hagiopolite liturgy
is the best explanation for most of the content of Q 19-1-33*.
4) He follows a Christian usage in composing a section on Zachariah and John the Baptist as
a preparation for the section on Mary and Jesus, following a Christian usage. Besides, the
striking parallels between both sections (2-15 and 16-33) [see Annex 2, pp. 31-32] suggest
that Q 19:1-33 is not the shortcoming of a complex editorial process, but a text with a
striking unity, and whose organization follows a very precise intention. 5) He practices Christian typological exegesis. If we include the section on Abraham, we shall conclude that he also knows the “cycle of Abraham”.
6) He has a remarkable homiletic talent, being able, for example, to merge episodes like the
questioning and presentation of Jesus in the Temple in a unique narrative, using the literary
device of Jesus speaking from the cradle. This implies that he knows at least some of such
“cradle miracle” traditions, which are attested about Jesus and other prophets.
7) He certainly has some knowledge of Aramaic (at worst indirect, but more probably
direct). This is confirmed by a play on words made on the name of John the Baptist (19:13).
The text reads wa-ḥanānan min ladunnā, “and a mercy from Us”. The word ḥanān (an hapax
in the Qur’ān) does not mean here “grace”, or “tenderness”, but “mercy”, like in Hebrew or
Aramaic. And note the name of John in Hebrew: Yoḥanān, i.e. Yo-ḥanān, “God is mercy”. The
word for “mercy” is visible also in Aramaic Yuḥanan, but it is of course absent in the usual
reading of John’s name in the Qur’ān, i.e. Yaḥyā, and it seems a bit far-fetched to look for it
in the Christian reading of the same rasm, Yuḥannā. When the Qur’ān speaks of “mercy”
elsewhere, and especially in this surah, it uses raḥma (Q 19:2, 21, 50, 53).
8 ) Since the Jerusalem liturgy was in Greek, either he has a good command of Greek, or he
belongs to a multilingual circle where some people can translate or explain the Greek
liturgy to non-Greek speakers. Palestinian monasteries, famous for their multilingualism at
this time, seem a good place for that.66
9) He is familiar with the literary genre of the soghitha (another hint to his knowledge of
Aramaic), and chooses to compose a kind of “Arabic soghitha”: the piece is, from a literary
point of view, remarkable – this implies he was an Arab, or was perfectly bilingual.
10) His knowledge of Christology is good enough to enable him to write a text of convergence which could work as a kind of biggest common Christological denominator. Were he less apt, he might have added unwelcome ideas for at least one of the parties involved (mu’minūn,67 Chalcedonians, Miaphysites, Nestorians). He is of course also familiar with some of the texts and convictions which circulated in the movement of the mu’minūn.
11) Nothing suggests that he relies on oracular words of Muḥammad. Thanks to his intimate
knowledge of Palestinian Marian liturgical traditions, he composes a dialogue hymn,
following the model of hymns which were sung or recited in a (Christian) liturgical setting.
It is highly unlikely, to say the least, that a scribe corresponding to such a profile could have
belonged to the Meccan or Medinan circle of Muḥammad – or more generally to the Ḥiǧāz,
except if we are ready to imagine Mecca or Medina as an Arabic Edessa, Antioch, or
Jerusalem. The most likely explanation is that this author should be situated elsewhere than
the Ḥiǧāz – most probably, indeed, not too far from Jerusalem, since he was extremely
familiar with the Hagiopolite liturgy. Besides, such a skilful text requires various specific
competencies, and we should wonder how they could have been acquired. The obvious
explanation is that our author belongs to the class of the religious literati. In other words, he
was certainly a Christian monk, who “converted” to the new faith, or put his pen at the
service of the newcomers – certainly, therefore, after the conquests
I agree here with Pohlmann (2012:185), except that I prefer to put converted between inverted commas, the confessional borders at this time looking too fuzzy to speak of “conversion” without any precision.
Dye, The Qur’ān and its Hypertextuality in Light of Redaction Criticism
https://www.academia.edu/12358270/The_Quran_and_its_Hypertextuality_in_Light_of_Redaction_Criticism 
Topic: Qur'anic studies today