Chrome has dominant market share. If this takes off and Firefox refuses to adapt some websites might just become completely inaccessible.

Right now websites can only make an educated guess because the ads don’t load, they don’t know whether you’re running a blocker or if you’re human.

Combine a more reliable mechanism with the guise of making the web safer and it might be more widely adopted; sites might refuse to load entirely until the check passes. This might mandate having any extensions disabled that can interfere with the content loaded by the site, this goes beyond ad blockers - could also be accessibility or other UI related enhancements.