Hi everyone.
I wrote my own article that drilled down into this sentence a little bit more.
The tl;dr is that the source, it seems, is Orosz (aka Pragmatic Engineer) referring to some leaked channels.
https://news.ycombinator.com/item?id=33483273
If this is true, and I am open to anyone correcting me because someone commented it was also in the NYTimes, lines of code was not the sole metric, and Elon Musk floated the idea of using it (rather than using it concretely).
This isn't to say that I'm defending (or, for that matter, criticizing) Elon Musk's actions or this article. I also found an article on India Times about how Elon Musk asked everyone to print their source code for Tesla engineers to review, which just seemed a bit odd to me.
But I've been seeing a lot of buzz about this on HackerNews and Reddit, and I haven't found very many original sources. Their conversations kind of make it sound like Elon Musk simply found everyone on GitHub and immediately fired whoever had the lowest line counts.