Childhood. Friends. Never. Win.
That is 100% not true.
Childhood friends win a lot. So much to the point that this "childhood friends never win" trope is a pure lie.
In fact, if you actually analyze anime/manga, being a childhood friend is actually a non-factor in if the girl will win or not....
In the end, it's random girl that's not a main girl never wins...
Being a childhood friend is never for or against anything. It's the position the childhood friend is in....
Childhood friendship is just a cheap way for the author to build up the relationship with no work....
If she's a main girl, it gives you an avenue for her to have her relationship without needing to build it up. If she's side character, it's an extra heroine with no effort needed....