Many "X_on_Y" type tags have unclear definitions like "when X is interacting sexually with Y" or even "when X are depicted sexually with Y".

This is pretty ambiguous. What exactly counts as sexual interaction or being depicted sexually? For instance does deep/french kissing, butt groping or similar count if it is obviously erotical, or does there need to be intercourse?

And to make things worse, I have found out that not all X_on_Y tags have similar definitions. Some say "X depicted engaged in romantic and/or sexual activity with Y", "When X is depicted romantically or sexually with Y" etc.

In the past, X_on_Y tags used to be for erotic/sexual situations only, and not for normal interactions.
I'm not sure when that was changed (inclusion of romantic activities) but I think my interpretation is this:

• Sex is NOT required for X_on_Y, it can be erotic or romantic.
• A couple holding hands, hugging, going on a date, or any other "normal interactions" is NOT X_on_Y.
• A partner playfully teasing or groping another's butt (in a non-erotic/romantic way) just to make them flustered is NOT X_on_Y.
• A partner playfully shaking their butt at another (in a non-erotic/romantic way) is NOT X_on_Y.
• A couple kissing/french kissing or cuddling in bed is X_on_Y.
• A partner teasing or groping another's butt to arouse them is X_on_Y.
• A partner presenting their butt to another to arouse them is X_on_Y.
• A couple engaging in sex is definitely X_on_Y.