Sure but reading the guidelines that Apple representative was clearly mistaken. Unless they said "we acknowledge what the guidelines say but they are incorrect", it just seems like poor developer relations comms (from Apple, never!).

I can't find the bit from the dev you're referring to so don't know if they have screenshots of it in writing or something, however, what I suspect is more likely (based on my experience talking to Apple reps about similar things) is that they gave a very charitable description of their feature, and the rep gave a non-committal "sounds like it could pass, try submitting it".

I don't get why the developer is so convinced that their tip system for tipping people based on their activity on their app is not tipping for "digital content". Unless you can only tip randomly with no control over who it goes to, or tipping is for the user's activity off-app, digital content (i.e. posts etc) are literally the only thing you could be tipping for.