No, pay attention. What you have read is "Halsin gives off the vibe of wanting long-term commitment (even says and is referred to by the game as such) - so it is extremely unsatisfying that he is then unwilling to commit"

This is not "Halsin has to be mono" this is "Tav deserves agency in the romance, and there should be an option for long term commitment in more than a singular form dictated solely by Halsin".

Awesome that you have girlfriends. You are at no point Halsin's partner, however. He directly refuses to be your partner.

That is the deal-breaker.