I understand your confusion. I was having the same problem trying to figure out what happened, if it was wrong, when my friend who I broke up with, but his hand around my throat and squeezed. [Posted about it above]
I think the slapping incident is wrong. It's a definitively aggressive, hostile and fast motion.
It has been suggested to me, that in my situation, perhaps my friend was experimenting with some kind of 'erotica' game that I'm not privvy to because he wasn't angry or mean when he cut off my air.
But I def think the slap is out of order. [Not that I'm ok with the choke. It was super bizarre.]