Single rear drive surely isn't an insurmountable problem with an electronic traction control system. (Probably much easier to implement with electric drive as well.)
The single driven rear wheel was possibly more efficient though.
Anyhoo, they've confirmed the FWD change:
Aptera switches to front-wheel drive - listing 6 reasons:
1. Better weight distribution, which, in turn, maximizes stability
2. Improved traction during acceleration and in inclement weather wet conditions
3. More efficiency at higher speeds
4. Increased durability during the life of the vehicle
5. Improved noise insulation
6. Increased rear cargo space (without sacrificing front legroom)
As well, they've announced production delays:
Aptera likely to miss end-of-year delivery date - AutoblogGreen