The downside to this method is that since the resulting cryptographic hash and salt have to be in the resulting file, so there is nothing stopping someone from pulling the hash/salt out and bruteforcing it locally (as opposed to being able to ratelimit login attempts on a server) if they are so inclined and have the required resources.. which may not be that much in the way of resources as the tool uses 1000 iteratio…
Is it a downside if the password is a 100 characters-long string?
But in practise nobody uses 100 character long strings. Security is the intersection of real users with systems, not imaginary ones.