I'm not sure about that. Something must be flagged in the Act 1 party scene, because some dialogue choices result in Wyll saying "There will be another time for us." Then, when the party's over, you have the option to go to sleep thinking of him. If you don't choose the more romantic dialogue options, that choice when going to bed later doesn't appear. For the going-to-bed scene to have those two possible states, the game must have recorded whether you tried to initiate something. To me, at least, it feels way more likely that there's a mistake later in Act 2, so the game should be checking for whatever flag was set at the party but it's actually triggering for everyone.
I mean, the alternative is that the developers didn't want to close off Wyll's romance from people who didn't talk with him in the right way at the party. But why choose that approach for just him when it seems like every other origin companion takes into account what you did with them in Act 1?
Ah, so you can actually get the party dreaming option for Wyll. Then instead, his romance is the only one you can actually pursue without starting it in act 1.
He is the only companion who doesn't have an option to start it outside of the party, that might be the reason. Lae'zel and Shadowheart get an approval based dialogue option that starts it, Gale gets the weave scene during a long rest based on approval, Karlach gets an unavoidable long rest cutscene based on approval. Astarion's the only one I'm not sure of because he never likes me enough in act 1, but I think it's similar to Lae'zel and Shadowheart. Wyll never got any dialogue option for me and I never got to kiss him at the party so I assume he's like Lae'zel - if you are already on the romance path for too many others before triggering the party, he's not interested (at that point, anyhow).
