I also like it. I think its bc the person is almost a blank slate emotionally and sexually and has no prejudice toward who they could like, so who they end up liking is so focused and pure, with no thoughts to gender or identity, just pure love. This is not to say that those that fall in love in line with their sexuality aren't in true love, just that its nice seeing a character with truly no preferences just happen to fall in love with another naturally.
Yeah they can prolly figure out a label for themselves later in a realistic sense but for the romance genre factor its cute just to witness these things without always having to go through the usually negative experiences of being queer. Not saying those stories are necessarily all depressing but variety is fun
Depicting sexualities clearly is nice but i really like when a completely inexperienced character who never bothered to think of these things like sex n romance just falls in love and doesnt have a specific attraction to any gender or identity just seems to like that one person. Stuff like this mostly happens in fiction but its still so cute haha