If that's why you have a limit then please go and change that immediately.
No, this post is talking about having a minimum length on the password for safety reasons (i.e. a limit on the minimum entropy). You're right that a minimum byte length will ensure this, but what happens when your user types in n-1 "things" but their password gets accepted anyway. That's only a minor thing but (and I'm not entirely sure whether this is possible) what about when your user types in n "things" but the password doesn't get accepted because it's actually only n-1 bytes. Now the password won't be accepted and the user has no idea why.
I agree that these are relatively trivial things, but the point is that it's not as simple as "just use the byte length".
No, this post is talking about having a minimum length on the password for safety reasons (i.e. a limit on the minimum entropy). You're right that a minimum byte length will ensure this, but what happens when your user types in n-1 "things" but their password gets accepted anyway. That's only a minor thing but (and I'm not entirely sure whether this is possible) what about when your user types in n "things" but the password doesn't get accepted because it's actually only n-1 bytes. Now the password won't be accepted and the user has no idea why.
I agree that these are relatively trivial things, but the point is that it's not as simple as "just use the byte length".