"NTR in no way says a character has to be with one guy."True but it is an inferior way to do NTR from a story perspective and there are reasons for that.
Like i said would you consider someone dating/fucking a prostitute or "town bike" after you ntr? if you have an emotional link to that prostitute? If no then in practice if they were to do it your way in one update you could have any of the MC`s girl fucking multiple dudes each day a different dude,and now they essentially became public property ,you can`t use them again for emotional link ,a big part of NTR is build up which builds a stronger emotional link ,corruption AND conquering the MC`s girl, if they become public property they essentially became unconquerable, you now have 2 key things missing and have left only corruption.
Different characters stealing diferent girls could work, however given the ammount of work it would take to build each one of those diferent male npc`s up and given how far and few between updates come ,and as we have seen with this update, honestly it would have been better to just have gotten only Becca content and get at least one sex scene than dilute it with other characters and get none.
"Kinda seems very cucked to just stick with one character" but it kinda doesn`t because then you would have build up and Darnell kinda has that more than any other character that is a "rival" to the MC , which is why scenes involviong him would carry more emotional weight and greater corruption .
And it would also makes the MC`s girls reusable for more scenes from an NTR prespective.