I think part of this ends up in the nuances of 'seeing someone.'
I'd probably break most dating into 4 stages:
Stage 1: Early/non-romantic.
Stage 2: Mid./knowing each other better.
Stage 3: Late/growing closer to each other.
Stage 4: Committed relationship (open, exclusive, or otherwise)
Most 1-3rd dates probably fall into stage 1, and it could be argued so do FwBs. Stage 2 would probably be where folk start to talk about more of their history and present, including dating and whatnot, but still with no commitment. This is where I would expect disclosures of this kind, what they expect/looking for from a relationship, etc., happen. This could last months, if dates were occasional. Stage 3 would be really delving in, talking about life goals, kids, marriage, what the future might hold, while also continuing to test compatibility and getting to know each other. Finding out about any surprises now would be pretty hurtful unless something was made clear in an earlier stage. It would likely blow up the burgeoning relationship for most people, unless things were above board. Stage for is making it official. If the couple hasn't defined themselves as monogamous, open, sharing, poly, etc., they were doing it wrong. This is the back end where it really isn't dating anymore, but being in a relationship.
One thing for the dev I hadn't really thought of because of the genre (AVN), but if this is a more realistic slice of life project, then addressing sexual safety is definitely part of that first stage of things, especially if people aren't considered/expected to be monogamous. I think most AVNs avoid it for a lot of small reasons, but it is a real consideration on the more serious side of things. That said, the vibe I got off this project was more on the fun side of realism, and prophylactics and safe sex talk can probably be handwaved in those circumstances. But I do recall it being satisfying in another AVN (can't recall which one atm) having a LI talk about using the toilet after sex to avoid UTIs. Sometimes the extra realism can be rewarding, sometimes it can get in the way of the fun.