My read: "we're not YC alum ourselves", since that would obviously be the first thing they'd say to engender trust.
Funny how that changes how I think about this. If they are in the YC family already, definitely more trust. YC alum abide by a certain code. If these guys aren't YC alums -- just some random guys -- then very different implication.
I personally wouldn't use this unless these guys are verifiably YC alums themselves. Otherwise, if you're an applicant - would you really want to trust some random dudes with your plans for world domination? If you're a YC alum - do you really want to pour time into something with unclear motivations and actors?
My $0.02. Probably being too cynical.
Edit: Ooof, the "I’m an investor, can I access your user base? The short answer is maybe." doesn't make me feel any better. Seems pretty counter to the YC spirit for there to be a side-hustle on paying-it-forward / helping each other.