OK but let's look at a couple more factors. Did you know that the 4680 pack on the Austin Y still has strong battery regeneration after being charged to 100% ? See Youtube video about that here:
This only happens when the pack is software locked to a lower capacity.
Also, Tesla has only ever introduced new battery cells 3 times.
Model S (18650) and Model 3 (2170) : In both cases, The entire car was brand new, so they tested the motors, wiring, HVAC, software at the same time as the battery. But for Model Y (4680) the car is mature with 3 years of production already. Only the battery and front casting is new. So they can slowly test the new battery while producing cars for customers and ramping up 4680 cell production.
Let me pose a question to you : If you had designed a new long range 4680 battery pack with 300 miles of range, would you:
1) Release it with 300 miles of range, which competes with your Fremont Model Y? Or would you
2) Release it with 279 miles of range, only software limiting 7.5% of the pack, which allows the Fremont LR Y to continue selling with higher range, and allows for longer battery endurance and performance and supercharging testing.
Prediction : The Austin Model Y is a Long Range Model Y with 300 miles range. The remaining 7.5% battery capacity will be unlocked, along with acceleration boost to 4.2 seconds, as soon as they can produce enough 4680 to switch over Fremont to 4680 LR Y. Then both factories will build the same car. Maybe Model Y Performance will stick with 2170 for now, with the large pack and 303 mile range.