Semantics, semantics. If you mosh into a system, you wouldn't also ssh into it. In that sense, the use of mosh replaces the use of ssh and mosh would be used in similar scenarios.

The neat thing about mosh is that it doesn't rely on ssh. All you need is a way to launch a process on a remote machine and securely transmit a shared key back to the client. ssh happens to be a useful way to do this, but it's not required

It only uses ssh for iniating the connection to leverage the authentication.