I 100% agree with this: the lesson to be learned from getting older and being burned by bad code is not that no code should ever be written badly, but that you should learn how and when to care, and by how much. I think too many experienced programmers have been subject to problematic code that they pre-emptively try to make everything bug-free, and very often times that's a huge opportunity cost.
However, there's a slight problem: We don't need that level of solidity. The rest of the stack is comparatively less solid, so his time would be better spent getting ten easy, frequently-hit bugs out of the rest of the codebase, rather than get one unlikely-to-hit bug out of his.
He hates producing code that's not up to his standard, but when our fleet of cars consists of a Lamborghini he built and a beat-up Yugo some other guy built, I'd rather my friend changed the rusty oil of the Yugo rather than make sure that all the bolts on the Lamborghini are within tolerance.