In password security, the longer the better. With a password manager, using more than 24 characters is simple. Unless, of course, the secure password is not accepted due to its length. (In this case, through STOVE.)
Possibly indicating cleartext storage of a limited field (which is an absolute no-go), or suboptimal or lacking security practices.
I like it that the site says the max length…this is not common. I wish it was.
The problem is a password hash is a fixed length regardless of the password, so if this is implemented correctly there is no need for a maximum password length. These things raise my security flag because it makes me think they are storing the password in plain text instead of doing proper practice and storing the hash only.