Multi-version approaches to developing software aren't as good at reducing common-mode failures as many people expect[1].
[1] J. C. Knight and N. G. Leveson, “An experimental evaluation of the assumption of independence in multiversion programming,” IIEEE Trans. Software Eng., vol. SE-12, no. 1, pp. 96–109, Jan. 1986, doi: 10.1109/TSE.1986.6312924.
All the electrical steering columns designs I've seen have used redundant sensors (often groups of them) specifically for that reason. The physical steering wheel to the shaft is still a SPOF, but it's also a "dumb" part where the only failure cases are mechanical. Eliminating failures there is straightforward engineering.
Yeah, I should have spent an extra 10 seconds thinking of the problem here and I'd have realised you can have multiple sensors going to different software on one steering column...
