Now for star citizen.
As I said cry engine has a little package for simple vehicles like the grey cat which is a rudimentary mechanical driving model. But the apc had nothing to do with it. What the apc does is it completely splits the chassis from the wheels. The chassis runs on it's own behavior and the wheels have an independent code to "look like they guide it on the surface"
This becomes very clear when you look at what the chassis does when the vehicle runs over an obstacle for example. It does something no chassis of a wheeled vehicle ever does in real life or simulation. It stays still. There is a ton more indicators for this lack of actual mechanical connection between the wheels and the chassis too, like the lack of harmonics, the lack of feedback into the chassis etc. But the most telling thing is really that the chassis doesn't care if a wheel is fully compressing it's suspension.
I asked myself what would result in such behavior and what keeps the chassis in it's vertical position and the answer is as disappointing as funny. It's the same IFCS monstrosity that keeps the ships and the hover vehicles going.
IFCS is a strictly high order system. This means it doesn't care for details like mechanical parameters. You tell the ifcs "how something moves" not what keeps it moving that way. This means the entire mechanical simulation is floating. It's parameters don't matter. What matters is how you envision something to look like and the IFCS will use whatever it has available to achieve that movement pattern. This means that a spring might force 10 kilonewton between its ends at a certain compression, but when it gets compressed more it suddenly goes down to 0.1 kilonewton. This behavior is impossible for a spring, it goes against what a mechanical spring would ever do. But it is what the IFCS tells the spring to do in order to achieve a certain movement pattern.
This focus on the movement instead of mechanics is very similar to how a drone like a quadrocopter works, or a robotic arm. This kind of aproach to a full on vehicle simulation though, apart from the very strictly limited realm of zero G spaceflight, will always result in nightmarish and unsatisfying driving and flight behavior.
This use of a high order IFCS system is why the chassis doesn't give anything about the position of the individual wheel. And this is why the Rover can just into low earth orbit occasionally like the nox does when something goes haywire.