This argument is continuing to ignore the solution that's already used to handle new APIs that are unstable and might not be ready: allowing developers to opt-in to deployment on that platform via standard metadata included in apps/extensions. If there was a concern with things being unstable, that would be the first thing to go to! There's already support for similar things. Creating special whitelisting is something extra that had to be done. Given the "we have too much work" angle here, I find it hard to understand why the existing mechanisms weren't extended instead of creating a new one.

It seems very funny to say "we had to give up and release a broken browser" and in the same breath take on extra responsibility for API correctness prior to letting any one who can't convince Mozilla to whitelist them to use the APIs. And take on responsibility of maintenance of a whitelist