How is it possible for Maps in iOS 13 to have location permissions set to "Whilst Using" but provide navigation instructions in the background?
Solution 1:
Taken from this Apple Developer article:
"In general, iOS apps are considered in use when they're in the foreground or running in the background with the background location usage indicator enabled."
Since the navigation is still in progress, the App is running in the background and therefore considered as "in use".