Decouple hidden fields for custom post types

[Vraja Das]

When editing custom post type with block editor and removing the metabox, our metadata is not saved.

• Edit a custom post type using block editor
• Comment out line 81 in class-metabox.php:

// add_action( 'add_meta_boxes', [ $this, 'add_meta_box' ] );

• Edit focus keyphrase or other metadata and try to save.