Is there a way to clear storage on a specific app on mobile?
The Reset App action on Android resets the application storage.
For iOS the only way to do it is by reinstalling the app that can be set using this option in Test settings inside a Job:
seems like it will not do it if you have FB integrated sign in - it stays in memory and the behavior is different from device to device. Using Pixel and Samsung it will store in memory so that you can use the same FB login over and over but on a Blu phone it will present user with login screen.