I've never heard a single SpaceX fan suggest that Musk actually writes code any more. I think that is a bit of an exaggerated caricature. He knows how to do it, and he wrote a lot of code in the early days of Zip2, but since then, he has left the actual coding to others. (And, given he hasn't done it in anger in over 20 years, his software development skills are likely rather rusty. Plus, I’ve never heard any suggestions he has skills in avionics software development in particular.)

I think he does actively involve himself in engineering-level discussions and decision-making, both at SpaceX and Tesla. Most CEOs don't do that, but some do – Bill Gates did that a lot when CEO of Microsoft – so it is not unprecedented. Designing something as complex as a car or a launch vehicle (or an operating system or an office suite) is a team effort, it is never going to be all on a single individual, and senior people are inevitably going to delegate a lot of the detailed analysis and design work to their subordinates – but a senior executive who actively involves themselves in engineering decisions can have a real impact on the outcome, for better or worse. He isn't formally trained as an engineer, but he has a degree in physics, and he is obviously a reasonably intelligent and very dedicated guy who has had years of access to some very experienced engineers, so the idea that he has learnt enough aerospace/automotive engineering to actually make a useful contribution as an engineering decision-maker isn't unbelievable.

I'm a bit of a SpaceX fan myself, but I feel like there is a big disconnect between what the average SpaceX fan actually believes about SpaceX, and the caricatures that many SpaceX/Musk critics like to paint. (Of course, there may be the occasional SpaceX fan who takes it way too far, and for whom these caricatures actually become true, but I don't think the vast majority of us are actually like that.)