advanced custom fields – Prevent block from being used in main editor, use only as inner block


I am currently using the allowed_block_type filter to control the available blocks in my theme, similar to the following example:

function acf_allowed_blocks($allowed_blocks, $post)
{
    // Register core blocks
    $core_blocks = array(
        'core/buttons',
        'core/heading',
        'core/image',
        'core/list',
        'core/paragraph',
    );

    // Register custom blocks
    $custom_blocks = array(
        'acf/test-block',
    );

    // Register plugin specific blocks
    $plugin_blocks = array(
        'gravityforms/form',
    );

    // Specify block groupings available on specific post types
    switch ($post->post_type) {
    case 'post_type_example':
        $allowed_blocks = array_merge($core_blocks);
        break;
    default:
        $allowed_blocks = array_merge($core_blocks, $custom_blocks, $plugin_blocks);
    }

    return $allowed_blocks;
}
add_filter('allowed_block_types', 'acf_allowed_blocks', 10, 2);

While this works perfectly, I am trying to determine whether or not it’s possible to remove the gravityforms/form block, but allow it inside the acf/test-block. Currently, if I remove the block from this function, it’s also becomes unavailable as an inner block in my ACF block markup, which looks like this:

$allowed_blocks = array( 'gravityforms/form' );
echo '<InnerBlocks allowedBlocks="' . esc_attr(wp_json_encode($allowed_blocks)) . '" />';

Does anyone have any idea on whether or not this is even possible with the current state of Gutenberg? I can just as easily live with it being available as both a main and an inner block, but it would be my preference to only use it as an inner block.