I'm hoping they have some goodies coming to awd owners at some point. Like even better range than rwd lr due to optimized motor operation.
The rear motor is the more efficient one. Every time you're using the front motor you're less efficient. So the "most efficient" AWD mode would be front motor off. In which case you've got a RWD with extra dead weight on the front axle.
RWD>AWD for efficiency because physics.
The S doesn't work this way because it doesn't have a higher efficiency PM rear motor like the 3 does.
How come the website says RWD and AWD is the same weight?
Go here. At the very bottom compare the models. Switch between the models.