In brief...
NTR is controversial. For lovers, it's very specific. For haters, it can range from... any situation where a woman is with another man or group of men at any time.... to the actual deed with or without MC/Player awareness of it.
It was simplest to tag sharing as NTR in most cases for players who wish to avoid it as well as those who love it. If what happens does not meet the threshold lovers were expecting "actual NTR", it's simply due to us trying to cater to as many players as possible. The balance is tricky.
Thank you for the feedback. We do appreciate it.