It doesn't work against which threat model?

Yeah, if you've got corporate espionage going on this isn't going to stop someone from lifting your slides and taking them elsewhere. But the most common culprit of corporate information security violations isn't a spy, it's a well-meaning employee who didn't hear, remember, or correctly interpret the request to not record the meeting.

Blocking the most common way in which this kind of well-meaning but ill-informed employee would break the expected security rules does work. It's just getting flak here because people are imagining a much more exciting threat model.