I won't say that there are any actual NTR in the game. But this game has a huge focus on Sharing/Swinging.
This is not my comment but this will make your doubts clear.
Dunno if ch 2 has the most, but the thing is, like you said, for every sharing scene you get with the switch on, there's one you get for switch off, so both paths are valid, and you don't feel the difference too much. Plus, Ch 2 just sucks anyway, might as well skip it
With chapter 4 the dev is just saying "fuck you" to ppl who play NTR Off, and not giving them anything while NTR On gets scenes. Nowdays, NTR Off is just a lite version of the game with less content. Not to mention all the naked touching other dudes, exibitionism, and even the single forced sharing (you are forced to triple threat Jessica in both paths) that bleeds into NTR off. There's just a lot less care given to NTR Off nowdays. At least for me, it feels like each update is making the game worse for people who don't like the sharing stuff.