When user is deleted from his default group, his new default group is not assigned in the intended order

group_user_del() function has
$group_order = array('ADMINISTRATORS', 'GLOBAL_MODERATORS', 'NEWLY_REGISTERED', 'REGISTERED_COPPA', 'REGISTERED', 'BOTS', 'GUESTS');
It appears this is intended to be the search-order for assigning a new default group to the user, but this array is never used as an index into $special_groups_data.
Therefore, $special_group_data is read in group_id order, so that order is used to select the new default group. Therefore, the user's defalt group is always Guests or RU.