I respect this point of view, let's see.
Regardless, I don't see any spoilers in this trap. I see an intention to fuck up the gameplay for some players. Besides that you can assume everything, it's no worse or better than looking for clues in renders, character words, or some other patterns. Even if your theory wins, you can't be 100% sure until event you theorized about happens in the game. The clue we are talking about, that can help with support of some theory regarding Quinn is not so significant to be a double trap you're talking about. Theories about the theories or traps is a quite new level, no shit
Why you asking me? I can't know that. And why you switched to Sarah and restaurant at all? We talked about fucking Quinn before committing with J&M and difference between sex during CUM-petition and sex on the roof. Both is possible w/o joining the restaurant and always free, btw, except 3-some with Riona and her. Your MC can agree to use the restaurant, but never use it, for example. Then what? Or you may use it selectively, only with Riona and Camila, but, for example NEVER fucking Quinn at the same time. And a lot of other permutations. Sex with Sarah, especially after camera reveal is a special case.
There are so many unknown variables in this equation that it's hard to guess how this major choice in general or ordering certain "dishes" can affect anything and when or why.
If you want my opinion, sex with Quinn is nothing, even for J&M branch. At least until you haven't agreed to use the restaurant AND bought some dishes there. If MC agreed and never used it - nobody have any evidence (well, Quinn have, but it's just her word), just MCs conscience. Everything beyond that tends to numerous possible outcomes and consequences and not only for J&M branch, I suppose.
Maya is not obliged to like any of the girl MC fucks and approve that. Especially, BEFORE they got into relationship and took obligations. "No strings attached" it was. Without conditions, like "but don't touch a Quinn". And again, all those potential sex with Quinn happening even before "no strings attached" announce. After the library scene Quinn is autoblocked (seems like by MC himself, because Quinn hadn't any clue about what's happening between J&M and MC). At least it's obvious that fooling around with Quinn is not "compatible" anymore and that Maya wouldn't like that (and after EP6, Josy too). Also, technically, it looked like killing the extensive and unnecessary and early branching. Same goes for teachers with J&M active path. Players see it as MCs conscience and kind of internal attitude change. But... it doesn't happening on Jill path, for example. While both paths are quite "romantic" and MC acts very specifically while being on any of this paths.
Regarding Tommy and the rest... MC is able to tell them truth that he slept with more than 10 girls. What was the punishment? -3RP (or -2 if you drink) and no new variables. Yes, the history of MC sexual adventures is saved anyway and DPC can always return to this in the future, but "anybody but not Quinn" in this context looks at least inappropriate and stupid, because MC fucked her before the Throuple was created. No guilty and no cracks in relationship. Don't forget that it's still an AVN game and that it must follow some patterns. I probably use AL as an example again, bc this is the best and closest in this case, because the game is from the same author, not just the same genre. In AL you can fool around till commiting with Megan/Melissa and a bit more in case of Rena. If you will continue to fool around or better to say cheat after taking obligations, then MC relationship is broken at the end. You may fuck the main antagonist (Leah) w/o consequences, twice. BADIK made it safer, since you can't fuck the "bad girl" after the particular point. The only possible issue here is restaraunt.
I'll tell you what it was. DPC decided to add the "Girls stats" feature. Some kind of QoL improvement. And it was a really cool feature, because if you have a multiply saves it's very convinient one to check what you have done and where you may fucked things up. Instead of reading tons of BIOS etc. But this sexual expirience looked ridicolous w/o some of the scenes, which hadn't considered as sex before or better to say hadn't considered as ones during drinking game with J&M. So, one improvement fucked up "safe" runs of some players. I doubt that he would change anything in drinking game if he hadn't implemented the "Girls stats" thing.