There's no mention of Apple in the original article. and the article and statistics are referring specifically to Linux the kernel - not "Linux" the GNU ecosystem.
Original article: "Those figures also don't include companies like Google which rely on Linux-based systems for their own technology, but tend not to contribute code back to the kernel."
Register article: "The likes of Google and Apple were notably absent from Corbet's list as, while both companies use Linux-based systems to build their tech, neither have a tendency to contribute code back to the kernel."
So whilst Apple do indeed use lots of components of the Linux environment and that's a valid point the register article could be discussing it's nothing to do with the kernel which is what this report was referring to.