Red flag!
You'd be amazed to know the kind of things folks think it's just normal.
I understand your point but I think clients want to do those fetishes without being judge and specially with someone hot they just can't get for free on Grindr.
I think that kind of question sounds like someone at dinner saying: Tell me about yourself... is just waaay to open.
I get the feeling trying to find out by text what he wants would be like "pulling teeth",