Along the same lines, there doesn't appear to be a way to ask for Tester info for previous versions. If you click on a particular version either using the TestFlight or the Activity option, you can navigate to a particular version, but there is no way to get the tester list with sessions and crashes for that version. THis makes it difficut to follow up with individual users regarding their crashes or to determine which testers have used the app a lot.
Under the TestFlight menu option, the left menu has an option for External testers, that produces the tester list and an installation (or invitation) date for each tester, but it doesn't indicate which version they installed. The list also shows then number of sessions and crashes, but only for the most recent version.