There’s no sense in using the init hook because this hook will be triggered on each page load.
If you want to update pages’ status every time when someone updates a field, you can use any of the following hooks:
- acf/update_field – this filter hook fires every time when a field is updated before it is saved into the database. This hook is a part of the ACF plugin.
- update_post_meta – this action hook fires every time when a field is updated before it is saved into the database, but it is a part of the WordPress core.
- updated_post_meta – this action hook fires every time when a field is updated after it was saved into the database. This hook is a part of the WordPress core too.
The first one passes four arguments into its handlers: $value, $post_id, $field, $original. You can learn more about it here.
And the last two hooks pass four arguments into their handlers: $meta_id, $object_id, $meta_key, $meta_value. You can learn more about them here and here.