I thought the author’s point was pretty well-made. Some implementations are so far removed from the original’s goals that they no longer count for it even though they’re technically a match.
It’s merely an oddity that ChromeOS is based on Linux; it could be based on anything else and it wouldn’t change anything. It doesn’t work like Linux does and you can’t use it for most of the things that make Linux worth using.
Even Windows (via WSL) is more Linux at this point than ChromeOS is. Let that sink in for a moment and you’ll see why we don’t count ChromeOS.