In the same theory, someone would need your EC SSH key to do anything with an exposed SSH port.
Practice is a separate question.
Wireguard is explicitly designed to not allow unauthenticated users to do anything, whereas SSH is explicitly designed to allow unauthenticated users to do a whole lot of things.
It's slow to scan due to ICMP ratelimiting, but you can parallelize.
(Sure, you can disable / firewall drop that ICMP error… but then you can do the same thing with TCP RSTs.)
I'm sorry, what?
If you're blanket dropping all ICMP errors, you're breaking PMTUD. There's a special place reserved in hell for that.
(And if you're firewalling your ICMP, why aren't you firewalling TCP?)