Earlier quoted context omitted.
Technically, but not usefully. It depends what you're trying to communicate. ChromeOS is based on Linux but most Linux enthusiasts aren't going to consider it Desktop Linux. The website is clearly catering to a Linux enthusiast market so the numbers communicate the right thing for its readers.
This just quickly descends into a "no true Scotsman" argument. https://en.wikipedia.org/wiki/No_true_Scotsman It's a Linux kernel and a Linux userland on top of `glibc`. It's not a weird libc, like Bionic in Android. You can run a Debian container and Debian apps; my own ChromeOS Flex machine runs Firefox and DOSemu. It's a Linux. It's the most successful desktop Linux there is, and so of course all the advocates dec…
Linux is two things: a kernel and an ecosystem of distributions. This website is clearly targeting users of distributions that brand themselves as "Linux distributions". In that way, ChromeOS is obviously not a Linux distribution to anyone that cares about Linux distributions.