yeah this is what i was getting at yesSo taking a deeper look, it seems that when Ian breaks it off with Alison over the phone, it sets their relationship to 3. He can apologize to bring it to 4. There are no more situations with her to raise the relationship score by the time she offers him to come to her place (after the Gillian thing). And the requirement for Ian to accept is 6 or more points.
So Alison's character is still trying her hardest to ensnare Ian, but Ian can't fall for it if he is on Lena route. Bummer.
my Commited Relationship to Lena Ian never able to accept Alison's offer to her house. He rejects automatically.
That playthrough also has that Ian went for Cherry on the first Shine scene, but she slept with Alison too.