It is possible, and the important thing to understand is that it is a different kind of routing with different capabilities, not the same feature applied to another protocol.
Modern proxies have two modes:
- HTTP routing. The proxy reads the request, sees the host header and the path, and can route on either. It can also terminate TLS, add headers, rewrite paths and load-balance on application-level rules.
- TCP routing. The proxy forwards a raw connection to a backend, seeing only bytes. Configured with a TCP-style entry point and a router.
SSH is not HTTP, so it can only use the second. That immediately tells you the limitation: there is no hostname in an SSH connection, so the proxy cannot route two SSH services by name on one port. It knows the port and the source address and nothing else.