Apparently, the this app maps provided are contained within Coverage , not downloaded on demand when accessing Coverage .
The good news: You don't need cell data or an Internet connection to look at the this app maps.
The bad news: The maps are updated only when Coverage is updated. (They have added a subscription service which might change that, but most of us use Coverage once in a blue moon, meaning that the subscription price would just not be worth it) (Think about it: When would you use Coverage? Only when traveling AND when you may be considering switching cell phone service)
But that is a second piece of bad news: As of this writing (16-Aug-19), the current version of Coverage is for iOS 10. This means that those of us still using iPhone 4S or iPad 2 (iOS 9) are stuck with out-of-date this app maps.
Given the structure of Coverage , I do not know how they could fix it, if they wanted to. I do know that, as a reference tool I might use once or twice a year, I do NOT want to get involved with a subscription service.
On the other hand, on my iPhone SE, I fully expect that the this app maps are up-to-date.
I just have to stop using Coverage on iPad 2.