The idea is, if something hardcodes e.g. /bin/grep because it was written on a system where that's where grep is, it will suddenly start working because now gre

The idea is, if something hardcodes e.g. /bin/grep because it was written on a system where that's where grep is, it will suddenly start working because now grep is also accessible via /bin/grep. So it's compatibility in the sense of making things work (instead of failing over pointless differences), not in the sense of being the same.