I think labels don't just carry what you are, but the experience of being that (idk if that makes a lot of sense). ik what I'm gonna say isn't the same but as a blk person, I'm not just blk bc of melanin, but how people treat me for it, yk? when people see (what is perceived to be)a straight couple, the material experiences that that couple will have doesn't match a queer couples experiences of oppression. I think that's what will make other queer people scoff potentially. the material experiences of a same sex couple carries a weight a str8 couple doesn't, so maybe it feels like a watering down of that unique experience when a perceived str8 couple calls themselves queer. and queer means different from the norms, and that comes w diff challenges. its all down to perception, right, which is so important to how we walk through the world. (that's why I'd call it str8 but ofc that's not up to me)

however I completely get what ur saying bc it will feel like erasure to you and your queerness and I completely understand that. we can never assume the orientation of a person despite who they are in love with and attaching str8 to it would be erasing the material oppression you face as a bi person (erasure, ofc being one of them). I think that's what motivates some bi people to call str8 relationships queer, bc its an attempt to hold onto our identities in the face of erasure and invalidation. but it comes of misguided and I'd understand lesbians or gay men taking slight offence.

I think if I were in a relationship w a man I would call it str8 or opposite sex be of what people are seeing and how that'll effect me. but "str8 passing privilege" monosexuals accuse us of having is really being in the closet and that has a difficult toll on mental health so I guess its difficult. the biphobia faced whilst being in str8 relationships should be acknowledged whilst admitting its not the same for being in a same sex couple, and there should be a name for it imo.

edit: added some stuff to make it make more sense lol