What are some examples of that for web standards?

FLOC/Cohorts API, AMP, Manifest V3, Widevine, WEI.

None of those are web standards. They are web technologies, but they arent standards unless other browsers agree to it.

So pray tell, what should the browser do? Just sit on their hands, like Firefox? That's a classic example of how a browser could be mismanaged.

Widevine is absolutely a web DRM standard. Literally every major streaming service uses it.