Actually that's not it, to put it in simple terms in netori you are screwing the girl, in netorare she is getting screwed in front of you instead. Does that make sense? There is no "forced" intercourse otherwise different tags would apply...
So in the end all these netorare terms boil down to the matter of perspective. A situation where there is a guy fucking a girl in front of another guy. It can be both netori and netorare depending on which side you imagine yourself to be.
Like someone has already mentioned previously, netorare or cuckoldry is actually niche...fetish? I am 100% sure most people imagine themselves in the main role, not as observers.