I'm missing the part that justifies what we see in that video. He's unable to mute the detectors, but there seems to be a distinct lack of smoke.

Why are people carrying water for this idiocy? Nothing in the document you linked has anything to do with the subject at hand. Fine, whatever, you're not supposed to be able to mute the detector in the presence of heavy smoke. But there is absolutely no prohibition against a mute feature in general.

I found a citation that I think even you will accept:

https://community.nest.com/message/36003

True, and the 4% business was also mentioned in the summary document earlier. That doesn't change my two underlying points: (1) it's an incredibly stupid regulation that seems to have been designed to cause people to remove the battery or otherwise disable their smoke detectors permanently to avoid nuisance alarms; and (2) there was no smoke at any level in this scenario.

Poor engineering on Nest's part led to a situation where a poorly-thought-out regulation came into play. Neither condition is defensible... yet look at all of the people in this thread trying to defend one or both.

(Yes, I'm moving the goalposts to a certain extent, as I was mistaken about there being no law against silencing a smoke detector in the general case.)

Worse, municipalities are starting to pass stricter code, requiring the battery to be unremovable:

http://rules.cityofnewyork.us/tags/smoke-alarm