Yeah but it's set in the operating system, not in the DJI app.
The way it typically works nowadays is that the operating system provides the mapping functionality, not the app. The app just tells the system "draw me a map of location X at zoom level Y", and the system does the actual job of fetching and managing map tiles.
The whole purpose of that is precisely so that any map loading and caching is done only once by the system globally for all apps installed on the device, instead of each app loading its own data like in the past (saving on the related network usage, storage requirements and battery drainage involved).
The OS will use many things like where you live, where you work, which areas are more frequently visited or loaded (by any app) etc to determine what to keep in cache, for how long etc and is thus in essence unpredictable.
Apps may or may not still have the possibility to manage things on their own, I'm not up to speed with the latest developments on all platforms anymore, but I remember a year or 2 ago when some services were switched to not being accessible outside of the OS handling anymore to encourage/force app developers to go through the system.