Yes... however it is a good estimate number for calculating the battery size. The A/C load on hot humid days in South Florida eats up battery especially pre-cooling the car when parked under the noon Sun.
I have Owned Rivians the last 3 plus years and have driven 40k plus miles . The average is around 2.2 Miles/kWh. These numbers are based mostly on Highway driving in South Florida. I think a better approximation for the Scout battery size should be miles/2.2.