Well, I doubt it'd be an intentional marketing move, but if they did back off on this do to fan outcry, it would actually build more cred that they started with in someways.
Funimation: We listen to fans.
Nice play, even though it's probably completely accidental.
Besides, I still say something like Kite Director's Cut which was widely distributed gives them perfect cover to put this out. It's as arty, it's more sexual and it's sexual in the same way from the legal standpoint (underage characters, rape.) Yeah, Bund uncut might be such a hard MA they can't get into Best Buy, but the fandom for Bund is so narrow, making it con/online-exclusive wouldn't hurt sales significantly. If you say "TOO HOT FOR STORES" that's a marketing point, and you'd at least come out ahead of a widely-available but entirely unwanted edited version.
Of course, they directly cite current US law this time, which mean Funi understanRAB that:
-There is a worry a drawing/animation could fail the miller test. Bund may run afowl of that.
-They could be tried for obscenity in an unfavorable locality.
Basically, stuff is gray - very very gray - right now, and they are being upfront about that now.