Chrome OS is 100% a distro by induction, because Gentoo is a distro and Chrome OS is based on Gentoo.
As for Android: I’d say it is a distro, but most people think of desktop or server OSs when they talk about distros these days. Obviously it’s neither of these.
KDE Neon is a testing vehicle for new KDE software. The devs don’t consider it a distro because it’s not meant to distribute anything. It’s for testing and they don’t (have to) beyond that. So this has nothing to do with how this OS behaves, looks or whatever.