Yep, it looks like you are right. I was passing along second hand information that I never bothered to verify. After some Googling I learned apparently Tesla only hides capacity at the low end to prevent a user from being stranded. The default settings also prevent charging to 100%, but that is fully transparent to the user.

Thank you for looking! I've seen this "Tesla sandbags at the top" repeatedly on HN but you're the first person to respond when challenged.

BTW the car won't actually let you drive at low charge, so yes, you can be stranded because the car refuses to damage its battery. That's why it comes with a towing service.