As others have said, it's not speaking USB - it just happens to be the same shape. But it's probably not a coincidence that it's compatible with a USB socket. In this case the designer wanted a socket that had 4 pins and could be hotswapped fairly regularly. USB sockets satisfy those criteria, are cheap and are easily available. It's pretty common to find standard connectors re-used for other purposes in the embedded world (I've found SATA connectors in some extremely strange places), so it wouldn't surprise me if tearing down this dishwasher did reveal an actual USB socket.