I guess car travelling would make the larger size not as relevant, but then that kills the density and feel of a megalopolis which tends to be central for most cyberpunk universes. I mean in theory, you could travel by car within one super large city, but there's no way they can put any amount of detail in such a large area consistently, so you'd have large parts of the city being just roads with generic NPC and generic buildings and shit, and then one random quest appartment complex that can be explored in the middle, until you go back to the "quest hub" which would be the actual cool place.
I don't know, I guess we'll have to see but I don't think driving around fake city stuff is very interesting. I do trust them to be able to pull off some serious cool shit, I'm just curious how they're gonna do it. Anyway this game is like several years away so whatever.