Whats to keep them from faking one?
Probably they screwed up and let an agent who is not in on the coup participate in the interview and he's the guy who wrote the original Form 302. So if they fake it, and he doesn't conveniently turn up dead, then they risk that he will say "hey, that's not the form I wrote". So they can't do that.
Note that the FBI has refused to make that agent available for congressional questioning for months now.