I thought that a minimum limit's there just to ensure sanity of a generator. You can't generally predict how a hash function will behave, but you can certainly define a minimum output length. What I was thinking about, that the restrictions are too strict, and there's a gap between what's secure and what looks secure.

I believed that it's generally expected that a password generator would produce passwords of a certain minimal length. At least I considered that nobody would write a generator (intended for a real-world usage) that'd produce, say, 3-character password for some edge case.

However, you sound reasonable. This leads us right to the extreme case - should empty passwords be allowed? (Considering that the user will be bugged like hell before letting him to do so.)

I should think more about this.