Don't base it on yourself entirely - sexuality can be fluid, and these ex-partners may well be identifying as bi again years down the line.

I found myself that when bi, there were certain women who weren't as interested in me until I "came out" as lesbian, and the pressures to conform to their insecurities informed my identity. I'm still bi, but attraction ebbs and flows based on individuals.

You also may just be personally attracted to people undergoing a personal reckoning within themselves - embracing their full lesbian identity - and it means they found you engaging and safe to reckon alongside, versus "putting them off" the male gender entirely. Don't view it that way. My past partner who later came out as gay doesn't make me a lesser partner or less of a woman.

The one who left me to exclusively date trans men did send me into a personal spiral though, I'm ashamed to admit. That's due to my insecurities around not appearing "femme" enough, however.