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I'm not sure there's a difference, really. The situation itself is clearly not specifically Japanese, and even less specifically otaku—you can find those things in dirty magazines sold in combini, and it would be surprising if it hadn't found its way into some JAV or other. It's not limited to pornography either (you can find it in shoujo manga as well, say), although the NTR abbreviation itself is probably overwhelmingly used in reference to ero.

On the other hand, the prevalence of “crush-only” netorare in otaku-targeted publications is more idiosyncratic, I guess.