It's not the reason, I read the raws and I know it's not the reason, don't wanna explain so u won't get spoiled, If u wanna spoilers just ask and I'll write it down
I want spoilers, can I have spoilers?
As you could see in manhwa Ilya noticed the system, so in the raws Jerry one way or another explains everything (I think) about system and the routes and love interests, so Ilay decides he will love him without Jerry choosing him as a route, and the route window opens occasionally
I like your theory btw, maybe It's the genuine brotherly love
Y’all think the reason the eldest brother’s route got deleted is because he acknowledged him as a living individual instead of a character? like he accepted that he loved him outside of the restrictions of the system