Yeah, it's kind of an unusual dynamic. They are official in the way they act with each other. Kissing, making out, showering, bathing, and the such... but never actually made anything official. That was part of my "ish" reply, yes but no?
Erynn does clearly want it, even if you disregard her thoughts. On the beach date when she catches herself with the ".... my boyf..." and the MC was too stupid to hear and react to it. That'd have been a perfect spot to have sat down with her and at least discuss where they stand with each other. Instead of these awkward moments that crop up. He's more than happy to comment openly and brazenly about the bodies of the LIs and their boobs, but can't tell Erynn that he like her or wants to date her when she talks about him being her boyfriend?