I'm not OP, but I think he means that the final decisions acted upon are not deterministic. So given an input, it won't necessarily produce the same decision every time.

For instance, if the model predicts with a 95% certainty to accelerate, then 5% of the time it'll do some action other than accelerating.

Deterministic code would be running under a hard real-time kernel such as VxWorks or bare-metal and would be designed such that all timing has fixed upper-bounds.

This involves reasoning about the scheduling of tasks to ensure that in worst-case situations, your timing requirements are still being met.

All safety-critical systems would be deterministic, you simply would not get certified otherwise.

Note: Theres much more to safety-critical application design, but basically, you have to be able to prove the behaviour of you code under all circumstances, which typically means no garbage-collection, dynamic-allocation, etc.

Not a real-time OS?

I'd guess it's about guaranteed response times (which is the definition of a realtime system - it must respond within the specified time). Since it's running a non-realtime OS, you could get arbitrarily long gaps in execution, which is not great for something that's driving a car.

Maybe they are talking about the numerical stability of the algorithms?