In his overview of the scholarship of the late Martin Hengel (who authored that the ascriptions “according to Matthew/Mark/Luke/John” were original to the gospels), James G. Crossley (himself, a very liberal New Testament scholar) noted that:
The authorship and titles of the
gospels are therefore very early, certainly by the last third of the first
century when Hengel believes they were written. . . . Hengel’s arguments are
strong in many ways and it is difficult to deny that the view of conventional Markan
authorship was present by the late first century. (James G. Crossley, The
Date of Mark’s Gospel: Insight from the Law in Earliest Christianity [Journal
for the Study of the New Testament Supplement Series 266; London: T&T Clark
International, 2004], 16)