Privileged ports isn't an example of security through security. Maybe you could call it security by convention. Still, it relies on a number of assumptions, none of which can be relied upon if a system is compromised, and if the system isn't compromised... well, you don't have a problem now do you?

Honestly, the only win of a using "privileged ports" these days is you don't have to worry about the odds of some other service randomly binding to your port. Since most systems spin up ssh well before they spin up services that bind to random ports, and generally don't ever shut down ssh, that isn't much a win, but either way, it is NOT a _security_ win.