Description

The initial state of a new post type is defined in WP_Post_Type->template. This initial state is acknowledged by the block editor when creating a new post/page/etc but not in the site editor.

Step-by-step reproduction instructions

1. Register a post type block template for a post type that appears in the site editor. We'll usepage (but you could use wp_block). Place this in a functions.php or plugin file:

function myplugin_register_template() {
    $post_type_object = get_post_type_object( 'page' );
    $post_type_object->template = array(
        array( 'core/image' ),
    );
}
add_action( 'init', 'myplugin_register_template' );

2. Start a new page from the regular dashboard, which loads the block editor, and you'll see the initial block content (an image block) in the post content.
3. Start a new page from inside the site editor - you'll see that there is no initial block content.

Screenshots, screen recording, code snippet

No response

Environment info

• WordPress 6.5.2
• Gutenberg 18.1.0

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes