[Plugin: User Spam Remover] automatic deletion if no input on custom post types?

Post types are just posts with a different value in the post_type column of the wp_posts table.

So, the plugin won’t remove the user if they have created any custom post type item (a page, an image, or anything else that WordPress stores this way). If the user is the post_author of anything in the wp_posts table (even an unpublished draft) then they won’t be deleted.