One of their points in the article was how they've decided to use more of the native OS interfaces instead of implementing their own versions (!!). For instance

One of their points in the article was how they've decided to use more of the native OS interfaces instead of implementing their own versions (!!). For instance, using the OS's native threading library instead of writing their own. So, the number of LoC kinda start to make sense when you think about them re-implementing some not-trivial chunk of an OS's native functionality.