Did that once many years ago on a Linux system, wanted to delete a directory tree, but I was logged in as root and didn’t realize I was at the root prompt. Wiped out the whole drive. Not a big deal since it was just a test install so I was being careless anyway.
Back then Linux didn’t protect root from making stupid mistakes. I think now you need another switch to actually delete the root directory. I’ve since gone to using FreeBSD mainly and I haven’t tried it there, but I think at root as root you can still wipe the drive with that command. FreeBSD is less idiot proof than Linux. I think iOS is based on BSD Unix, isn’t it?