@KZO As he's not supposed to, seriously. the story is not like Idol pretender, Most of the mc's development has been with the heroine, this guy has hardly showed up. So much that these chapters here feel a bit forced. Even the Student Council President ending would be a more believable ending that the Best Friend one.
"Isn’t it funny how people are fine with a gender-bender that has a “yuri”ending, but if the gender-bent “girl” accepts being a girl and falls in love with a guy, they consider it yaoi and drop it immediately?"
That's because hormonal feelings have no place in magical transformations. An ending that forces(and in these stories, it's always forced, they never try to write a normal progression) the transformed male MC to end up with his friend always feels artificial, because it always goes against the true nature of the MC. The story always leave a feeling that the body is what decides who you fall in love with. Name any other gender bender that has a best friend ending and I assure you that the mc has no business going to this ending.
In Idol Pretender the MC took the drug because he wanted to be more manly, but his mind becomes gay instead, because his views imediately change to view his asshole of a best friend as a possible love interest, a clear cop out. In that one other series with Loki screwing over the mc(Edit: Boku Girl, I just remembered the name) becuase he was fun to toy with, that ending was atrocious because it was 100% a "last hour change"(with the character still liking the female friend), that one was worse because despite the looks, the mc was clearly straight and really loved the girl candidate throughout the series, he always despised being confused with a girl and having all boys trying to to date him at a glance, but he was pranked by a divine entity and became a real girl instead. In that one, i'd support a Loki ending over the main girl, but never the ending that the author went through.
Also, just notice that in these stories, the author clearly forces the feelings into the characters, by reducing and sometimes outright removing any interaction with the girls the main characters are supposed to love, shoving the "best friend" character into literally every possible situation, until the mcs mind changes to accept the guy. It's bad writing pure and simple. This makes it unbearable to watch because it's like the author is saying, this is what I want it to be, deal with it, it's not a natural progression. And so from the night to day, the MCs feelings for the possible heroine immediatly change towards the best friend, in the most artificial and stupid way. As if the mc is a guinea pig in a social experiment with fully controlled enviroment.