my point about affinity is that you need a certain affinity to start a path, not to end up with another
Throuple path have affinity check, but other LIs dont(well, Jill will reject you in ep8 if affinity is DIK, but its not required to start her path)
Throuple affinity check - EP4 library scene (Neutral or Chick) - but you may end up with ANY affinity though. You have time to start with DIK, then soften a little to become Neutral and after joining the Throuple go for a full DIK route.
Quinn affinity check - EP6 rain scene (DIK only) - but you may end up with Neutral or DIK affinity. While CHICK affinity is naturally blocked because you can't technically and "legally" have it at the end of EP8 if you got DIK aff in EP6. In short - you simply doing more than 4 DIK major choices anyway to stay on her path.
Jill affinity check - EP7 fight for her scene (Neutral or Chick). Having DIK affinity in this spot ends her path later anyway. Is it a check? Of course.
Only Sage doesn't have any checks or requirements. You may be a complete asshole to her for 7 episodes and have 0 RP and she will still try to throw herself into MC at the HOTs party in EP7.
what if you compare the requirements and different moments for all LIs?
1.Some variables prevents you from starting a path (BESIDES AFFINITY CHECK)
Sage(none), J/M(none), Jill(none), Bella(honestly I didn't check what happens if you fuck up cafeteria talk, so let it be 1) Quinn(1)
2. Path will end up if do smth wrong
Sage(none), J/M(none), Jill(picnic skip), Bella(Cathy scene), Quinn(Jill path)
1. Sage - agree. Literally nothing can stop this path. Potentially spoil the future (Jade, restaraunt), but not the start.
J/M - requires to fuck either of them or both to get their path. Lewd scenes variables are checked - obviously.
Jill - Kiss her back on their first date - path is fucked up if you don't (lewd scene variable). Picnic date, it's a decision packed into a variable - technically.
2. Think of it as of natural incompatibility and cutting the unneeded or even impossible sometimes branching. Also such conclusions is great when the whole game is finished and not when we are a bit past the middle of it (speaking of things that may fuck up the paths or even branches). Finally - Quinn is a side girl. So picking any MG branch somehow ends her path anyway, even if it's not a J&M and Jill. Further branching also starts to shut down. Nicole or Nora is the most fresh example. Closest candidates - Lily or Nicole. Riona or Quinn, etc, etc, etc.
as for not fooling around with other girls, then yes, anyone path became very simple, just chase the girl you like and be happy.
but game have option to date and fool around with multiple girls, and all major LIs don't care about it(well, except Bella).
Quinn is unique in this sense, because she is a side girl with main girl vibes. But that's all. Any side girls are hardly cut off if you pick one of MGs and vice versa.
I have a CHICK playthrough at the end of which there was an option to choose from all LI at once, and no one complained that I fucked or dated the wrong person in the process.
Sage & Bella mostly. It's not about "wrong" or "right" person. It's about the mess it creates at the end. Dumped J&M is best example. Even MC calls it a mess he didn't ever wanted to produce.
about Quinn's restaurant, I honestly thought it was necessary for her path, apparently I was wrong.
but how can you chase Quinn and not support her business?
If you would assume that she falls for MC, then she'd probably respecting that internally. Check her reaction during hang out in EP7, when she asks who from restaurant girls MC likes most and offers him a freebee. If you pick "Quinn" there she is definitely flattered. In weird and sick way (speaking of whole situation), but still.