This is the wrong number to look at. The relevant number is the login attempts that would have otherwise been successful. And if you’ve disabled passwords, that will be 0.
If failed login attempts go from 0 to 1000 in a single day, that’s very interesting and likely means you are being specifically targeted. You’d notice that if your ssh port is, say, 7731.
With exactly the same targeting, on port 22, you will see a rise from 100,000 to 101,000 which will likely not notice, despite it being as dangerous.
Changing the port does not make a targeted attack any more or less likely, or any more or less successful. But it does make it much more visible - and that’s useful for security as well.
A fault in your reasoning assumes that you know exactly what the attacker does - a credential attack; indeed this is the most common. However, maybe they are trying to exploit a zero day timing attack, requiring multiple attempts? Or some reconnaissance that lets them figure out valid usernames?
The different port won’t stop these of course, but will make the attempts stand out - which may allow you to stop them if noticed in time, or at least understand them in retrospect.
This is the wrong number to look at. The relevant number is the login attempts that would have otherwise been successful. And if you’ve disabled passwords, that will be 0.