Yes, but the only way to interop multiple scripts on a POSIX filesystem is to use UTF-8. I can forgive people for not realizing that filenames in POSIX are a weird animal: they are NUL-terminated strings of characters (char) in some arbitrary codeset and encoding, but US-ASCII '/' is special.

EDIT: Also, "considered UTF-8 by default almost everywhere" is... not necessarily wrong -- nowadays users should be using UTF-8 locales by default. Maybe "almost everywhere" is an exaggeration, but I wouldn't really know.