The biggest issue I have with developing Gutenberg Optimized themes is different reviewers have different or inconsistent test data. Theme Unit test data (which is out of date) and Block Unit test data (which is out of date) is not sufficient as reviewers often have their own test data without which we are unable to replicate or fix any inconsistencies.
All we end up doing is going around in circles trying to fix bugs that we can’t replicate in any version of Gutenberg holding up the review queue as we submit and resubmit after making “guessed” CSS changes to fix a Gutenberg styling inconsistency for a single reviewer and then doing it all again for a different reviewer.
I have no issues with the review process or the reviewers, I’ve always found them to be fair and reasonable but in order to alleviate the frustration for developers and reviewers we should all be testing and developing with the exact same test data.
I suggest as Envato developed their own version of theme check, they also produce and maintain their own Envato Gutenberg test data and all themes are tested against that data explicitly.