So as leymannx pointed out in his comment, the “delete_post” hook actually handles both scenarios I was looking for, as it seems to know to run a “for each post deleted, do x” when “Empty Trash” is clicked and will also “do x” when “Delete Post Permanently” is clicked!
My final code ended up looking something like..:
public function wcmdl_remove_deleted_location_users(){
$currentpost = get_the_ID();
$parentid = wp_get_post_parent_id( $currentpost );
if( get_post_type() == 'dealer_location' ) {
//do stuff involving $currentpost and $parentid here...
}
}
Keeping in mind that this is being used within a standard plugin boilerplate format and NOT directly in the functions.php file of a child theme, this hook was placed in the “includes>class-[plugin name].php” file..:
$this->loader->add_action('delete_post', $plugin_admin, 'wcmdl_remove_deleted_location_users');
If you were to be trying to do the same via your functions.php, the structure for this would instead be:
add_action('delete_post', 'wcmdl_remove_deleted_location_users');