> The chance for a bit flip to affect a critical path that is noticeable by the player is very low, and quite a bit lower if you design your game to react gracefully.

Nobody does

> There's a whole practice of writing code for radiation hardened environments that largely consists of strategies for recovering from an impossible to reach state.

And again, nobody except stuff that goes to space and few critical machines does. The closest normal user will get to code written like that are probably car ECUs, there are even automotive targeted MCUs that not only run ecc but also 2 cores in parallel and crash if they disagree

Sure they do, you just have to think about it a different way.

It boils down to exception handling, you don't expect all of your bugs or security vulnerabilities to be known and write your code to be able to react to unplanned states without crashing. Bugs or security vulnerabilities can look a lot like a cosmic ray... a buffer overflow putting garbage in unexpected memory locations vs a cosmic ray putting garbage in unexpected memory locations... a lot of the mitigations are quite the same.