If an attacker compromises the server and gets hashes, yes it could matter.
A 20 character password is for all practical purposes mathematically immune to being brute forced.
And, this doesn’t even take into account dictionary attacks. You don’t need to brute force every character permutation a lot of the time, you just need to brute force words.
a) when humans generate passwords, they are not perfectly random; they are memorable, which means they often use dictionary words, which are vulnerable to dictionary attacks
b) even if they use moderately good passwords, that can't be broken with the dictionary, there's a high chance of password reuse, and many passwords have already been leaked
c) when password managers generate truly random passwords, they run into exactly the problem in the article
You are so focused on the math of the situation, you ignore the practical realities.