I think in interlude Zoey told Emma boyfriend that she started exploring her body with fuckface. (It was choice) which kinda indicate Zoey was only sexual with fuckface. I am not sure if Josy even met Vinny or any other diks before coming to b®. Dpc doesn't really write his stories complex, for now I am just going to think that Vinny was there because pink rose stop buying from him and probably to see all the new faces. From fuckface flashback Zoey was always a loner and mostly spend time with fuckface. (he used to stay at her place sometimes) If anything happened between her and Vinny, it must have happened in San Diego. (Which is unlikely since Vinny and Quinn was a thing at that time)
I agree with you. Personally, I also always take this decision so that they have explored each other's bodies. In this case, I even assume that Zoey has only had sex with one guy so far. But that doesn't rule out something else. What if Zoey has also explored her sexuality with a girl. Oops.
I can imagine so there is a hidden decision to that. DPC himself wrote in his Q&A so that there are inconspicuous decisions, but they become very important in the later.
Example.
Zoey can decide if Emma should send her photos to a guy or a girl and Zoey has a gay girl radar.
Then Zoey has explored the male body with the MC and maybe the female body with Debbie. She might be Vinny's sister and called Vinny that Zoey is at the party, so Vinny came to see an old girlfriend again. He finds out that his sister Debbie was cheated on by Zoey with the MC and is therefore angry with the MC.
It doesn't really matter which option is chosen, because in both cases Vinny will be mad at the MC.