Assuming the attacker doesn't have a leaked database of hashed passwords and therefore can't run the brute force on a local database. I want my account to be secure even if there is a leak which has been the standard for authentication for more than a decade.

This password should not be in any leaked database of hashed passwords, because it is completely randomly generated. You can't even set it.*

*unless you take this password after it's generated and start reusing it in other services, but that is pure self sabotage

It would be if Google's app password hash database was leaked.

Is there any public knowledge of a Google password hash database leak for any of their apps ... ever?

Good point, although if that happens, then I think we probably have a much bigger problem

Fair point