The way those filesystems do it is that they implement an allocator of resources beneath the actual "filesystem", so that you can snapshot things by marking blocks CoW and then allocating non-filesystem space for the metadata.
As it happens, ext and friends don't roll that way, so adding that functionality breaks compatibility with those filesystems.
Also, most of the new filesystems which allow snapshots in the way I describe have some awesome problems - like needing to truncate a file in order to rm when the filesystem is full, because the way the allocator structure works means that you can't know ahead of time how much space it takes to atomically delete a file, either...
You're just wrong.
NTFS itself is case-sensitive - the Windows interface on top of it is case-preserving and disallows collisions in case-insensitive cases, but NTFS itself allows multiple files which would collide in a really case-insensitive filesystem.
If you don't believe me, go mount a filesystem using NTFS-3G, make two files which would collide on a case-insensitive filesystem, and be amazed as it fails to panic.
Or, if you really want proof, go read the NTFS specifications about how it behaves in various namespaces.
I'm genuinely curious how you produced an AC's name.
"I may be synthetic, but I'm not stupid" -- the artificial person, from _Aliens_