Fabrication is perhaps too strong a term, but the separation between history and myth has not always been that strong. For example it was common (and accepted) to write stuff in some famous person's name.
I don't think it makes the content itself any worse, but it's difficult to know what was really historical.
I don't formally study this, but such problems become quite apparent when I try to e.g. find out historical sources for some philosophical statements or anecdotes. Probably not that different from how people attribute all sorts of "smart stuff" to Einstein.
https://en.m.wikipedia.org/wiki/Pseudepigrapha
Edit: by "scholastic fabrication" I mean that scholastics spent a lot of time "interpreting" especially Aristotle (and tried to make it compatible with the Bible). I'm guessing a lot of what we think is "greek philosophy" may be from these interpretations.