Is it possible to "update" an app in external beta testing in Testflight?

I'm wondering if it's possible to update an app in the beta testing external testers phase with TestFlight. Currently it appears that in order to update the app, I am required to upload a new build, turn off testing on the current build, and then submit the new app for external beta testing review, then I can invite external testers. This requires those testers to download a new version of the app.

My concern is that I would like to make weekly updates to the app based on user feedback during the beta test without causing the users to lose their data. This is a game, and I don't want the players to lose their data. It's a game so it means they would be starting over again from the beginning of the game (losing their progress).

Does anyone know any way around this issue?