The instructions in default.settings.php say
This variable will be set to a random value by the installer. All one-time login links will be invalidated if the value is changed. Note that if your site is deployed on a cluster of web servers, you must ensure that this variable has the same value on each server. If this variable is empty, a hash of the serialized database credentials will be used as a fallback salt.
but this explanation of salting says
A new random salt must be generated each time a user creates an account or changes their password.
and goes on to clarify that each salted hash (eg password) should have its unique salt stored along with the hashed+salted password in the database.
Am I misunderstanding the article I read on salting, or is Drupal using a faulty practice for the sake of convenience, or is the article wrong, or is there something else going on?