Yes, the content is created using the WP Editor. If you mean check the HTML of the block from the editor side, then it’s strange: It displays the markup as I would want it, yet when it is published on the front end it changes.
The HTML on the backend:
<figure class="wp-block-image alignleft size-large">
… …
</figure>
HTML generated on the front end:
<div class="wp-block-image">
<figure class="alignleft size-large">
… …
</figure>
</div>
I’ve reduced this test theme to the absolute minimum, just the basic files for the theme to work, so there’s nothing in the theme that should be interfering.
If I use the twenty-twenty-two or twenty-twenty-three theme the markup is correct, meaning it’s the same on both the back end and front end as i would expect it to be.