I don’t know how much of Corso’s book to assume is fact.
However, my relative who worked in the area asserted that most of it was fact . . . whatever that means.
It’s been some years since I read it, but their were a number of technical gaffes that I had seen that convinced me Corso pulled a LOT of his “work” out of his butt.
We ufologists have to be very picky with what we hold onto as data, or you can get caught running down a million bunny trails, most leading away from what we hope to find.