@aral this explains it better: Yes, it's confusing.
It's not 7 days of non-use, it's seven days of application use without visiting the site.
Safari is one application, the homescreen app is a separate application. Presumably, all the alt browsers or WebView apps are separate applications as well.
Since you can't use a homescreen app without visiting the site, the 7 days of not visiting the site can't happen. https://news.ycombinator.com/item?id=22688294