... What are you trying to say, exactly?
'Having sex' is different than 'a sexual act'.
If I bump into you in a crowd, and accidentally or intentionally quickly grope you, well, maybe thats a kind of sexual assault, or maybe its a genuine accident.
But if I grab hold and don't let go, untill you climax... well, thats different.
Surely you can see, consent or nonconsent aside, that the consistent amount of time dedicated to a, or a combination of sexual acts, at some point, it crosses over into a threshold and is now 'having sex' or 'fucking' or... whatever verb variant of 'fucking' thats more specific to the kind of fucking, 'fingering', 'blowing', 'eating out', etc.
Or, maybe I'm being way too autistic, and you're just making a pithy joke?