I'm a little puzzled by this statistic. Most scholars (faith-based and non-, apart from fundies) agree that the four gospels attained the form in which we now know them between 60 to 100 years after the events they narrate, or purport to narrate, and that they incorporate earlier texts and oral traditions. So speaking as a philologist, calling this language "non-contemporary" seems to commit us to a pretty exigeant sense of "contemporary."
A faith-neutral philological/historical study of these quite interesting texts teases out a number of layers in their construction. Any given passage is quite likely to incorporate formative elements from various layers. It's not like doing archaeology, where you shovel away the stuff on top to get to the stuff that's lower down and hence older. You just can't pare away Talmud from Torah that way in the gospels -- it's all mixed up. You can make some shrewd guesses about how earlier material was re-shaped by somebody's theological or polemical agenda, and even about what the earlier material might have looked like -- but you can't really ever get back to it in any definitive way.
BTW, very few people who know the languages and the texts and the scholarship, faith-based or non-, think that it's all just made up out of whole cloth. Everybody, apart from fundies, agrees that there are mythological and urban-legend elements there, but also that the point of departure for this elaboration of texts is a series of events that really happened. Backwoods Hasid from Galilee goes wandering around, attracting crowds, stirring people up, gets iced by the Romans, maybe with the enthusiastic cooperation of the Temple authorities, or maybe not -- this is a much-ground ax -- that's the arc, and there's a pretty good consensus that something like that is what started it all.