We do not have a QA team dedicated to the changes in Cucumber open. What we generally do is provide "release candidate" (which are beta version of the new major release to come).
For this new release, we've had 6 release candidates before cutting the 4.0 which were available for anyone to try out. In fact, we've decided that prior to any release of a new major version, we'd keep a full month between the last release candidate and the final release to ensure that people have enough time to try it out and provide useful feedback. We generally announce the release candidates on Cucumber blog and Slack channel.
Any feedback is more than welcome, so don't hesitate to help us (as you've already done with your previous message).
To provide a bit more context on the changes in the HTML formatter, we've started a new formatter from scratch, which is compatible and consistent accross all Cucumbers (Java, Javascript and Ruby). This explains that some of the functionnalities may have disappeared (but they'll be back, thanks to feedbacks like yours).