Yes thank you for confirming this, this is exactly how my Holly-Playthrough went too. But after some People pointed out it seems that if you choose Holly in Chapter 7 and want to continue with her you immediately lock her as your love interest and therefore you lose Lena in Chapter 8 and you lose every Romantic Option with Alison in Chapter 9. I mean I don't like that it goes that fast without even spending much time with Holly before but I get it because that's how a Relationship with Holly works.it's definitely a bug, I did a fresh playthrough focused on Alison while also getting with Holy so Alison and Jeremy never hooked up and Jeremy never said anything about a threesome, but out of nowhere Alison said that she met Jeremy and he proposed the idea of a threesome to her and that me and him already agreed on it, Bitch what? I never agreed on anything.
But the Threesome Part with Alison and Jeremy has to be a bug because like you said Alison never hooked up with Jeremy in the Playthrough you mentioned and Ian never talked with Jeremy about a Threesome (I think he even said he gives up on Alison since she has no interest in him?). Also what's interesting in this Scenario you just lose with Alison in both ways (if you say sure go ahead with Jeremy she gets really sad because she thinks Ian doesn't care if she does and if you say you don't like and want that she gets mad at him and you lose Points)