The hidden truth...
"We previously explored a signal that checked for interstitials that ask a user to install a mobile app"
And there, tucked quietly away, is the real reason behind this. Google do not want you using apps - they want you using websites and thus continually adding to their vast coffers of profiling information. And by hiding behind a claim of "removing interstitials", they can make this appear palatable to most people, including the IT-savvy, in exactly the same way as having carriers responsible for rolling out Android updates makes the idea of Google having control over said updates seem reasonable.
Just another step in the grand plan to create a monopoly and manipulate people into welcoming it.