alt Hacker NewsThis is a vacuous statement. No one is stopping me from using JPEG XL in the same sense that no one is stopping me from using DIMG10K, a format I just invented. But if I attempt to use either of these in my website today, Chrome will not render them.
In a very real sense Google is currently stopping web authors from using JPEG XL.
The web was designed from the start to solve this problem and you can serve alternate formats to user agents which will select the one they support.