Sorry for the late response. I mentioned Freedesktop in the context of the Linux desktop. Freedesktop is responsible for the desktop ecosystem typically associated with Linux, and it's what application developers refer to when discussing Linux compatibility. Steam for ChromeOS is not referred as Steam for Linux for a reason, it's an entirely different application. Of course, there are exceptions, such as NixOS and Alpine for example, but both of them still aim to be part of the "Linux desktop" ecosystem, whereas ChromeOS does not, and yes, it's "Linux" under the GUI stack, but referring to ChromeOS as a Linux desktop would only confuse those less familiar with the topic or worse, mislead them.