I think you are overly obsessing about the score. We don't know the criteria that Tesla will use to select testers, but my guess is that it will be something like:
- Everyone with a score between 80 and 92 will be put in the list as a potential tester.
- That list will then be sorted by a combination of:
- Average miles driven daily
- % miles on AP
- % highway miles
- % city miles
- % miles driven at night
- Geographic location
- etc.
Then they will pick off the top 100 to get access to the beta and monitor them to see how it goes. If all is well after a couple weeks they will re-do and add a couple hundred more, lather, rinse, repeat.
Note: IMHO: I think they will exclude people with a score above 92 because they know in normal driving you are going to have "events" and it shows they are trying to game the system, and you don't want those kind of people testing your beta software. (Maybe the cut-off will be 95, or 97, but I really think there will be a cut-off.)