The only reason I'm playing the game so far is because the dev said you can play faithfully...that's how I'm playing right now...as soon as that changes and something is forced on me, I'll say goodbye and wish you luck anyway...but so far it doesn't look like it and I hope it stays that way.
The dev did say that Suzy flirting is encouraged by Anon, and sharing her is optional for now.
(That might change in situations where giving a choice would significantly bloat the story route workload.)
So yeah, there's a possibility things won’t stay fully opt-in forever. If it happens, I trust it’ll be for narrative or structural reasons, not to force kinks — the dev clearly knows his characters well.
That said, like you, I’d probably stop if that boundary disappears.
But for now, I’m fully enjoying the ride while we still have the choice.