The theory is wrong. I just completed my test drive and the 100% - 0% capacity appears to be...72.3kWh...exactly the same (+/- error margin) from what I got last August.
I drove 327.1 miles on 68.69kWh (car UI) non-stop in 6 hours 9 minutes at 55 mph in 32 degree weather with the heat off (seat heater on high the whole time).
I began with a 100% charge which indicated as 325 miles and ended with 5% charge which indicated 16 miles.
When I stopped I was showing 327.1 miles at 210Wh/mi which comes out to the 68.69kWh capacity. Dividing that by .95 (how much battery I used) comes out to 72.3kWh if I took it down to 0%.
In order to get rated range (325 miles) it appears that you have to do 222Wh/mi. I believe all they did was change the rated miles constant...unless they found efficiencies in the inverter or other hardware.
The 100% range under these conditions (210Wh/mi) comes out to 344 miles.
Here are some relevant pictures:
Starting Charge
Starting range in-car
222Wh/mi is exactly rated range - 75 miles driven, battery is down to 250 miles (started at 325).
My half-way turn around point in Cape Girardeau!!
Cutting it close to the supercharger!
The final verdict
TeslaFi is reporting the drive differently and shows 201Wh/mi and 65.62kWh consumed...not sure why there is such a big difference.