Add the generated classnames to the output.

function wp_apply_generated_classname_support( $block_type ) {
	$attributes                      = array();
	$has_generated_classname_support = block_has_support( $block_type, array( 'className' ), true );
	if ( $has_generated_classname_support ) {
		$block_classname = wp_get_block_default_classname( $block_type->name );

		if ( $block_classname ) {
			$attributes['class'] = $block_classname;
		}
	}

	return $attributes;
}