> The Chromium team shouldn't have the absolute authority to shoot down would-be standards like this

I’m not sure that “the Chromium team” is a real thing. Chromium is a cross-company project. People from different companies and different teams work on it together. Google has a Chrome team.

edit: I’m not familiar with the Google JPEG-XL situation, but generally speaking, it should be possible to ship a feature in Chromium without Google’s involvement because there are three non-Google Blink API owners (last time I checked).