they've got no proof that Bill Buck knew it was a forgery
Bill Buck presented it as a fact.
It was not.
End of story.
Anyway, for him to have seen the e-mail, he would have read the thread with all the "this is probably a hoax" messages.
And he didn't exactly contact Fleecy to get confirmation that it was him that posted it either.
So he knewingly, and willingly, submitted something he didn't know the authenticity of, as evidence. Most likely he knew it was forged. Of course, he wasn't betting on Amiga Inc. suddenly being able to disprove this. Looks like Amiga Inc. got a good poker hand at last!
Not one claim that it (AOS4) was planned to be forged from AmigaDE.
Which didn't happen. So it is irrelevant.