Well I'm not an expert per se but it looks like one is giving it to another one who is then giving it to one who is pleasing a different one via mouth.
I have a rat terrier that spends all. damn. day. trying to fuck her toys. It's not even a sexual thing, it's like a dominance thing, she'll be chewing on a stuffed cow and then boom, fucking. Stuffed squirrel? Fuck it. Long tube with monkey face? Fuck it. She doesn't hump anything else, just her toys.
@niceengelman you sure she didn’t pick up that behavior from you?