Your right most people's definition of NTR is to broad.
NTR is psicological abuse. It can be related to sex or things relating to sex but it doesn't have to be. Many thing's considered NTR while having a psicological element are not NTR, and even have there owne culcher such as Cucking or S&M or Master/Slave.
NTR is very difficult to convey it's true meaning in context, even harder to translate.
For example you say to your girlfriend "you look good in that dress, my grandma has one just like it" is that a complement, an insult, or both?