Imagine actually self inserting in porn LMAO.
You're watching someone else fuck somebody that you're not. All porn is "cuckshit."
It is and playing such games is a soft form of cuckoldry. You are not a participant, you are a role-playing spectator.
But the topic with NTR seems more serious to me — you enjoy when you are cheated on, while as a cuckold it is a view from the outside