The issue here is we live in a time when trans identities, MY identity, is considered elective. It isn’t. It never was. It never will be. But my move to live authentically as a the woman I always knew myself to be has resulted in my sexual orientation label changing from ‘straight’ to lesbian. That I’m a gay trans woman is the greatest self truth I’ve known and finally had the courage to live. Yet cis lesbians view me with with suspicion because hello, transphobia - they still consider me a ‘man’.
Further, gender is the single most fundamental divider of humanity. It is applied to us 10-15 years before considerations of sexual orientation begin to dog us. When I go to the bank my being gay is immaterial, my being a woman far less so. I rely on that fact being recognised and reacted to by society because to do otherwise impairs my ability to function in society.
Being trans does NOT erase differing sexual orientations. On the contrary. For every story like Cassius’ here, and Elliot Page’s, there are stories like my own where the ranks of sapphic lovers are bolstered by trans women actualising their true gender identities.
So no I don’t agree with your statement that “…there’s a danger that the argument that “one can choose the label of their sexual orientation” can quickly be conflated to “one can choose their sexual orientation”.” Both can be robustly defended by promoting a little education of the differences between gender identity and sexual orientation and the intersections between the two.