NTR is for me another term for cuckolding, whereas sharing and swinging are seperated from NTR. In this game, the dynamics are clearly sharing. But that's just my idea of what these terms mean. For many NTR opponents, also sharing and swinging are part of their 3 letter nightmare.
in terms of sharing and swinging there's no arguments there what you described is the universal terms for these sex practices and fetishes, but to me ntr isn't another form of cuckolding, but just a fancy term for cheating done to you in real life behind your back or in a VN (not you doing it to another, i consider that vanilla cheating) by a wife,fiancée,gf,partner inspired from Japanese culture
don't get me wrong i like them all sharing,swinging,cuckolding, but my favorite is NTR = cheating done to you behind your back and eventually you found out about by gradually noticing certain behavioral changes from your partner and you slowly began to have suspicion so you investigate until you found out and confirm your suspicions
e.g. let's just say a woman cheating on her partner behind his back, for either she's not satisfied with him anymore so she cheat for sexual pleasure or she began to develop emotions for another person or other reasons, now let's say her partner is not into the whole sharing or swinging or cuckolding but like i mentioned above begins to notice and start to investigate until he found out by either hiring PI and have photos or video proof or he himself decide to follow her one day and see her with her lover in a restaurant, bar, his condo, whatever....
now let's view his options:
bust and confront them on the spot --> eeeeiiikkkkk not a fan
wait and prosses the what and why --> the way to go
1.she's either not in love with him anymore but can't bring herself to end the relationship for whatever reasons (kids,not a fan of divorce or separation) or him fore the same reasons
2.she's just having her fun and he decides to wait and let her have her fun for now, it's just a phase she'll grow out of
or him having the same rational
3.she's in love with both her partner and the man she's having an affair with
now either he confronts her and they reconcile and she ends her affair and maybe after awhile starts another one again or not, or if he accepts these circumstances (our love is strong she'll come around and stop) (let her have fun and continue to think i don't know) (the kids and i don't want to separate)
now maybe some consider this person to be a cuckold but i don't.
another examples: now let's say this person after finding out he got some sort of evidence by the form of a video or a photo and after seeing his partner cheating on him got conflicted ideas, (am i okey with this? am i turned on by it? am i whatever....? can i forgive her?) and decided to let her have her affair and think he doesn't know, which develop this psychological game with her thinking he doesn't know? if you think about it does that make him a cuck? maybe to most people but they don't know even the participants themselves think he doesn't know that's why they're doing it in secret if he has reasons she herself can't consider him a cuck because she doesn't know his reaction if he find out
oblivious doesn't mean cuckold, let say this person work 10 hours job and kids to take care of, and his partner getting action behind his back and very careful concealing it does that make him a cuck? nooo
now let's get to real life, let's just say i'm into sharing,swinging,cuckolding now it may take awhile but eventually you'll find a partner into these things as well, with the partner okey i can share her by talking to trusted friends or a stranger i met in a bar after he got tested, i can go with her to a swinger club and voila i can meet another couple to do the deed, i can find a dom partner and i'm weak willed enough for her to cuck me right in front of my face and later i find it hot etc...
you see how these fetishes are feasible in real life, except for the type of NTR (which is the true definition of the word) i described because you can't read other people minds and see from their perspectives
the only place you can get that specific high is from fiction (tv,movies,comics,AVNs) not in real life, it's the forbidden fruit and that's why it's the sweetest, to see from her perspective how the affair developed from the start and the psychological game at home trying to hide it