Gutenberg custom block using only register_block_type() and HTML

I have the following core block HTML

<!-- wp:group -->
<div class="wp-block-group"><!-- wp:heading -->
<h2 id="hello-world">Hello world</h2>
<!-- /wp:heading -->

<!-- wp:paragraph -->
<p>Lorem ipsum dolor...</p>
<!-- /wp:paragraph --></div>
<!-- /wp:group -->

Is it possible to create a custom block from PHP using that HTML? Similar to as I would create Patterns?

register_block_type() can be used to register blocks from PHP. Is it possible to simply pass the HTML to register_block_type() and create the custom block?