What is he doing?

I have 5 cats. All fixed. My 3 year old male is the bottom of the totem pole. Very happy being unimportant in the group hierarchy. Today I saw him grab one of the females by the neck. I’ve heard this can be a mating behavior. BUT he didn’t try to mount her. Instead, he flopped over, pulling her over too, and starting making biscuits on her back while he was still holding the nape of her neck.

What does this mean?

Mating and comfort behaviors mixed together?