That's filesystems, not the OS. There are some extremely good reasons to treat filenames as bags of bytes, which is why Apple got rid of case folding in APFS. Think performance, locale issues, etc.

(And before someone says it, yes, of course performance matters for filenames. Every single stat shouldn't need to worry about case folding.)

There's a big difference between being and actually making use of such anti-patterns. Especially on such a scale.

You can have macOS use case sensitive filesystems (like case sensitive HFS+), and you can have linux use a case insensitive file system (like FAT32)