You could wait to see if Homestuck contradicts anything in Gio's transcripts before worrying about whether they're fabricated, lest you wind up accusing someone you don't know of bald-faced lying without evidence. When this has happened before (ahem, emails,) all parties have wound up agreeing on all the facts and differed in interpretation. I think Gio is also too smart to post records he knew could be immediately and trivially contradicted; otherwise he has some big honking brass balls on him and wants to pick a losing fight for no reason.