My take of the OP's point was that the deep general stack was unnecessary and decreased reliability. My read was that they think your self driving car software shouldn't also be able to run arbitrary python scripts. My argument is that it's practically irrelevant to reliability. I would not be surprised if in the future you could download an app to your iPhone, connect your phone to your car, and have the app drive your car. Sure, maybe having a specialized real time o.s. without any higher level interpreters could be more reliable in the early days, but the gains from rapid iteration you'd get from allowing cars to be driven by apps running on higher level abstractions would be worth the trade off, and over time the latter could be iterated upon to achieve practically the same reliability as over-engineered systems.