user_save functionality doesn't match documentation

The Documentation specifies the following:

$account: (optional) The user object to modify or add. If you want to modify an existing user account, you will need to ensure that (a) $account is an object, and (b) you have set $account->uid to the numeric user ID of the user account you wish to modify. If you want to create a new user account, you can set $account->is_new to TRUE or omit the $account->uid field.

What it fails to say here is that you must add also $account->pass, $account->status, and $account->roles for this to function properly, and they must be the same as what is already in the current user object.

According to this documentation I should be able to build a standard object with just a uid property and have no issues saving a user.
The bit about roles is here:

      // Reload user roles if provided.
      if ($account->roles != $account->original->roles) {
        db_delete('users_roles')->condition('uid', $account->uid)->execute();

        $query = db_insert('users_roles')->fields(array('uid', 'rid'));
        foreach (array_keys($account->roles) as $rid) {
          if (!in_array($rid, array(DRUPAL_ANONYMOUS_RID, DRUPAL_AUTHENTICATED_RID))) {
            $query->values(array(
              'uid' => $account->uid,
              'rid' => $rid,
            ));
          }
        }
        $query->execute();
      }

The bit about passwords is here:

      // If the password changed, delete all open sessions and recreate
      // the current one.
      if ($account->pass != $account->original->pass) {
        drupal_session_destroy_uid($account->uid);
        if ($account->uid == $GLOBALS['user']->uid) {
          drupal_session_regenerate();
        }
      }

The bit about status is here:

      // Delete a blocked user's sessions to kick them if they are online.
      if ($account->original->status != $account->status && $account->status == 0) {
        drupal_session_destroy_uid($account->uid);
      }

And Here:

      // Send emails after we have the new user object.
      if ($account->status != $account->original->status) {
        // The user's status is changing; conditionally send notification email.
        $op = $account->status == 1 ? 'status_activated' : 'status_blocked';
        _user_mail_notify($op, $account);
      }