That doesn't really seem like the sort of thing that needs to be standardized at all, though. They're both valid, they're both readable to anyone competent, just do whatever feels right.

Mixing and matching them makes the codebase harder to maintain, especially for those juniors who we're supposedly concerned about.

I don't think it does. This isn't some big architectural thing where the choice actually has implications that reach beyond the function you're in. It's not even on the level of naming conventions, where you might have to go look elsewhere to see how something is named. If you can understand both of them, which you should be able to even as a junior (as you even imply yourself, by saying it doesn't matter which one you pick), you can read both of them just fine.

> It's not even on the level of naming conventions, where you might have to go look elsewhere to see how something is named.

It's similar to naming conventions - you wouldn't want to mix snake_case and camelCase in the same code - only more so, because it's a bigger leap from one to another. Things that are the same should look the same and things that are different should look different. If each loop in your program is represented differently, it'll be hard to understand.

> If you can understand both of them, which you should be able to even as a junior (as you even imply yourself, by saying it doesn't matter which one you pick)

Juniors can learn anything but they can't learn everything. The more trivia they have to deal with, the longer it will take to learn the big things. It doesn't matter in the same way that, say, it doesn't matter whether you pick Rails/Ruby or Python/Django for your webapp; it's still a bad idea to do both at the same time.