It could also give useful priors for targeted attacks, "Their password is 5 characters, and their daughters name is also 5 characters, let's try variations of that".

Some system accessible to hackers who can see the length of the password /and/ having a single 5 char password has a security of a key under a doormat.

Maybe this is far fetched, but you could get an LLM-based auto-research system to extract these potential relationships