Tell that to anyone doing high integrity computing certification with included liability clauses.
Who will show in court from Linux RTOS contributors?
Tesla has liability clauses about the life of people and if they trust linux then any other serious project can do so.
BTW why just the kernel? It's ad-hoc. If your critical software project crash because of any open source user space library such as e.g .NET core, it's no different.
It shows given the sad stories regarding their auto pilot "quality".