Pretty much. Also it's unfair to think that OPs are constantly checking in every second of the day to see if fillers have questions. I try to check my prompts every here and there and sometimes I have only seen a comment a couple of days after. If you are unsure if the Op will be uncomfortable if their fluff prompt suddenly becomes all about xeno tentacle sex and mpreg, just create your own prompt or don't include it all.

Yeah you are not the OPs servant, but if you are just going to derail and ignore the OPs feelings and do whatever you want regardless, then just write it as your own fanfiction and not a fill to someone else's prompt. That's equally rude in my opinion.

Maybe I'm just old school, but this feels like common decency, there is a reason why most of these more extreme kinks tend to usually come with warnings. They are not for everyone.