A site named Just Miniatures in the UK seemed to have been hit by the Google mobile interstitial penalty, when in fact, it probably should not have been. This is in addition to many sites that should have been hit, that did not see any negative impact yet.
Their interstitial is an age verification, which according to Google would not be hit by this penalty. Here is a screen shot:
The webmaster shared the ranking and you can see, their mobile rankings dropped shortly after the roll out. Here is that chart:
Google's John Mueller responded to the issue in the Google Webmaster Help thread saying "I've passed this on to the team to review. It's always good to get feedback like this!"
So if you see more false positives or even any other impact, since we are seeing very little now, let us know.
Forum discussion at Google Webmaster Help