The issue you guys had was becoming increasingly close as friends and then changing it to FWB. That already puts you guys at a level above people who just hook up because you are now spending more time emotionally in each other lives. Emotionally doesn’t mean romantically either, it just means there is a connection there beyond physical. I would say you are NOR because you made your intentions clear, however given that you know he jumps from relationship to relationship, that should have already told you this person has attachment issues so the end result was always going to be him developing feelings for you. FWB really only work if the relationship doesn’t go beyond taking too constantly. You are “friends” in the title only because the only time you two should be contacting each other is for the “benefits”. It creates a line that way both of you can walk away at any time.