I do wonder if you misremembered the wording a little bit. It's not 1/3, and hopefully they didn't say that. It's supposed to be 1/2. Here is the page and the wording describing it:
Supercharger Idle Fee
"For every additional minute a car remains connected to the Supercharger, it will incur an idle fee. If the car is moved within 5 minutes, the fee is waived. Idle fees apply when a Supercharger station is at least 50% full, and double when the station is 100% full."
So that is supposed to be idle fees only if the station is at least 1/2 full. However, you have noticed a problem they have frequently had. Whatever sensor readings they are using to get that "information" into their database utterly sucks. It seems that way too often, their support people have a screen in front of them showing that the station is nearly full, when out here in the real world there are tumbleweeds blowing through the 7 out of 8 empty stalls. So--yeah, you shouldn't have been assessed an idle fee at all, since it was less than half full.
Yes, it applies to
all Tesla model cars. Unlimited charging has nothing to do with it, because this is about when cars are just sitting there, blocking the spots and
not charging. No one has a right to unlimited blocking of Supercharger stalls.