
Why in all these BL mangas the seme is so against of bottoming? In real life many gay couples switch.

I'm not referring to that part but this (pages 16 & 17).
https://www.mangago.zone/read-manga/therapy_game_restart/mi/br_chapter-202995/pg-21/
Although it's not the case here (he's relieved though), it's common for the seme to refuse and even take offense if he's suggested to bottoming. I guess BL authors think that making semes the receivers makes them less manly.
Chada's art style is divine Everything look good with their touch.
What's the sauce of their work
Define the relationship, I believe.