Why do women behave so strangely until they find out I’m gay?

I’m 30, somewhat decent looks, smile a lot and make decent eye contact when I’m talking with others face to face, and despite being gay I’m very straight passing in how I talk/look/carry myself.

I’ve noticed, especially, or more borderline exclusively with younger women (18-35-ish) that if I’m like, idk myself, or more so casual, and I just talk to women directly like normal human beings, they very often have a like either dead inside vibe or a “I just smelled shit” like almost idk repulsed reaction with their tone, facial expressions, and/or body language.

For whatever reason, whenever I choose to “flare it up” to make it clear I’m gay, or mention my boyfriend, or he’s with me and shows up, their vibe very often does a complete 180, or it’ll be bright and bubbly if I’m flamboyant from the beginning or wearing like some kind of gay rainbow pin or signal that I’m gay. It’s kind of crazy how night and day their reactions are after it registers I’m a gay man.

They’ll go from super quiet, reserved, uninterested in making any sort of effort into whatever the interaction is, to, not every time but a lot of the time being bright, bubbly and conversational. It’s not like I’m like “aye girl, gimme dose diggets, yuh hurrrrr” when I get the deadpan reaction lmao

Why is that?

And

Is this the reaction that straight men often get from women when they speak to them in public?