But they aren't conflicting: they have the same goal (not running into stuff). In fact, there's yet another different, redundant, potentially conflicting safet

But they aren't conflicting: they have the same goal (not running into stuff). In fact, there's yet another different, redundant, potentially conflicting safety system: the human safety driver. If only one were to trigger, it still wouldn't be a conflict. And yeah, redundancy through using non-identical systems is very much a thing, and considered much safer than having two identical things (which might make the same mistakes). Source: I've worked on ASIL D safety-critical automotive systems, where diverse redundant subsystems were actually a design criterion.