I don't know about other gender benders, but this particular one barely qualifies as such. Because the MC is now completely okay with being Tatiana. He/she considers Tatiana's father and brother as truly their own family. And completely identifies as a girl. I honestly wouldn't be surprised no matter which gender the MC is attracted too and would even feel it's totally normal for Tatia to be bisexual because that's kinda of a given due to the whole situation.
We can't say for sure since there's no process of thought that went through the protagonist's mind when he switched body. He just went along with it for no concrete reason. A very fuck my old family these guys are now my family. Also weird how he just "I'm gonna honor Tatiana by making her a good person" but in reality he just took advantage of the situation to fix the trajectory of his life of become a proper pianist bc he had both the financial support and previous life hack. Feels more like he's using Tatiana's parents as a replacement to his actual parents and tried hard to have a good relationship with them so he wouldn't have a neglectful fam. From the way it is written he has no interest in romance for both genre at the start but in latest chapters and later in the contact with both potential love interestd changed that. Given he's once a man understandably he made Tatiana bisexual. While also not being unaffected by male characters kindness. Anyway so far she/he doesn't seem to be still much interest in romance but def is affected by both side.
I always feel confused with gender bend romances. Since it's a guy in a girls body is it a yaoi if he and a guy end up together? (because it's a boy's soul) Or is it yuri if he and a girl end up together? (because it's a girls body). Or should I call it the heterosexual romance? I'm not sure pls explain!(￣∇￣")