No, this is a low priority issue which TBH I don't even expect to see fixed, because it's a feature which was removed in v5, which is not really causing any real issues and last but not least, it's only affecting the 3rd party development process.
Shot in the dark:
Take a look at your core_themes database table and check if there are any styles at all and if at least one is set as default ( set_is_default column) !
You could use a tool like https://validator.schema.org/ or https://search.google.com/test/rich-results?hl=de to test your page to see what schema is returned.