Using my implementation of your Meta Box Block I can enable users to query other parts of the posts data as well. A very simple example for instance is a custom block that will show the terms of a category on the post. But for that, I will need at least the post ID.
Other things might be author of the post, publish-date, or pulling in other custom field (not block) field-data. That last one seems far fetched but why not if it can be done?
As you said, it works when rendering front-end. But that experience is somewhat off when, while using Gutenberg, I can't get to the post id and use that.