So, why the default namespace persist if I did all right? Would it be some javascript function of wordpress that would be doing the request on the incorrect route? What function? How to fix it?
If the endpoint works then you changed it correctly, but if you’ve flushed rewrite rules/permalinks, and it still isn’t working, then you need to raise a bug with the Gutenberg github, or the official WP Trac.
Note that this is assuming you’re only trying to change the REST API endpoint of a single custom post type, and doing it via register_post_type and the rest_namespace parameter with WP 5.9/6 or higher.
Otherwise, it looks based on this code that you have found a WordPress/Gutenberg bug with retrieving autosaves: