What I do find interesting is Alastor fully snarls at Rosie.
Like he's thinking about biteing her.
The closest he gets to doing that with Vox is this. Which I think he's just thinking Vox is cringe.
Also Alastor's ears might be down with Vox becuase he's uncomfortable but look at his eyes with Rosie.
He looks way more scared and unsure.
Also his body movement in the first don't you forget is way more rigid. Theoretically be has more freedom of movement but he's more stiff. I think he's like actually scared of Rosie in away he isn't with Vox.
Maybe thats a bit well no shit Rosie owns him how ever Vox is the one who actually shocks him.
I take this as Alastor thinking that anything Vox can do here is temporary meanwhile Rosie can throw him infount of anouther Angel that can kill him or hide him for another 7 years. Long term torment or death is worse to him then temporary torture.