a304470 created the issue

Change the s3 storage class works.

But there is an ui glitch: after selecting a different class, and the selector again is not grayed out, it still shows the previous class.
To verify whether the selection has worked one has to close the info window, deselect the file, reselect the file, reopen the info window.
Maybe hard to implement reliably because of timing, but still a nice to have ;-)