You can install Linux on Windows PCs without even needing to developer unlock, doesn't that mean they're as open as Chroembooks. Not to mention things like if the battery goes completely dead on some Chromebooks, Linux is completely wiped along with the data and replaced by ChromeOS. Also have to press Ctrl-D past a vscary warning on every single boot on some Chromebooks or flash a new bios.
Can Mozilla make a Firefox for ChromeOS? How many Chromebooks that are being dumped in the education space are having Linux installed on them? Google has root on ChromeOS and the user doesn't. The whole purpose of them is to force the user into uploading all their data into Google's cloud. That's why even a $1400 machine has a paltry 64GB of storage but comes free with a few years of 1TB space on Google Drive.