It's about managing a limited resource. And keep in mind, this is something that would only be in effect something like 1% of the time, only at SC locations that experience high demand at certain periods, and only if there were other SC's available within a reasonable distance. We are talking about a very specific and rare case, which I don't think is going to dissuade anyone from getting a Tesla.
Big concert lets out at 11pm, and the SC across the street has 8 stalls. All 127 Tesla's at the concert decide to hit the 8 stall SC. Whats a company to do? If there is another SC 5 miles down the road sitting empty, you can send the 127 drivers text messages informing them of that. If a driver needs to get home and has a 20 mile drive with 100 miles of range, you send him a text message letting him know that Supercharging isn't required. If a driver lives 80 miles away, and has 60 miles range left, and an SC is 40 miles away, another text message could be sent letting them know that. If the driver insists on getting in line behind 126 other Tesla's to charge even if they don't need to, then limiting them to a 75% charge is a reasonable thing to do. And charging them additional for the privilege of unnecessarily hogging a stall they don't even need is also reasonable.
The basic premise is that just because you buy a Model 3, you do not automatically have the right to use any given SC stall as a 24 hour free parking spot. There is a very large gray area between this, and the idea of dictating how much charge people need. Tesla would be stupid to not attempt to manage a limited resource.
RT