Sometimes friends are just friends. You could easily push the logic further, but I think it's too far-fetched to try to take this completely to the extreme and assume that ALL childhood friends in manga are romantically involved.
Even the nurse turned out to be childhood friends with teacher and in the same chapter, after resolving their misunderstanding from high school, immediately took him on date. With that, we're like 5/5 for childhood friends=couples in this manga. The only exception is Sakura's ex-boyfriend - ex, not current. And the whole "I want to be in the same high school as you, so I will study very hard to get your chosen elite school" is basic romantic trope.
No one denies that this is a manga about childhood friends pairings; it's the series' main running gag. But then again, you're trying to take it too seriously, generalizing it to ALL childhood friends in the story. Like the popular meme that all female characters in yuri are lesbians until proven otherwise. If you read everything as subtext or romantic tropes, you can pair any characters together. Even bitter enemies, because "from enemies to lovers" is also a basic romantic trope. But then again, if you want to ship them, that's your business. You don't need my permission to do that, lmao.
