One potential problem here is that this only applies to page blocking interstitials that promote an app. Page blocking interstitials that push signing up for a newsletter, for example, will not be penalized.

It could be hard to argue that an interstitial pushing an app (especially an app specifically for the site the user is visiting that gives them enhanced features compared to the mobile web version of the site) is more annoying, distracting, or otherwise harmful to a user than any other kind of blocking interstitial.

Thus, one might try to conclude that Google's actual interest here is trying to keep users from using apps to access content instead of using the web site where Google is more likely to be the ad provider.

I have no idea if this could rise to the level of an antitrust violation, but it's the first place I'd look for one.