Why staggered size 18" wheels front + 21" wheels rear on Cybercab Robotaxi?

[DaveF]

So the Cybercab robotaxi has smaller front 18" wheels and larger rear 21" wheels which gives it a stance and unique look, but is this an aesthetic choice or are there potential performance benefits from the staggered wheels and tires sizes?

Does this setup somehow improve the Cybercab's handling or ride quality? Maybe it somehow benefits range, efficiency, brake regeneration? Will this staggered fitment even be on the production Cybercab?

BTW here's the front and rear wheel tires specs on the Cybercab prototypes --

215/60R18 front tires
225/60R21 rear tires