Replying from a different account...
And yes, under normal circumstances, that's how it's supposed to work.
However, it is clear from working on this device (and reading the other responses) that the app/phone can have a glitch where the accumulated data does NOT delete when the account is removed and the app reinstalled.
I can vouch for this because I:
- Deleted the account from the device
- Offloaded the app
- Deleted the app
- Reinstalled the app
- Restarted
And all the data (15 gigabytes in this case) was still there. However, deleting and reinstalling repeatedly eventually removed the excess data. (Even though the app STILL says its using 15 GB... it actually isn't.)
It's a pretty weird glitch. But it's definitely a glitch and not user error.