Yes, it isn't absolutely clear what is "good advice". Yes, it might misfire and prevent useful content from being disseminated. Yes, the WHO is far from perfect. And yet, if I were the owner of YouTube, I would have to reduce the liability of having physical harm, or even human deaths, being attributed to content served by my product — regardless of how tenuous the connection between content and action would be, and how many disclaimers and waivers surround such content.
Collectively, it's a disgrace if all digital media adopt this strategy, because we would be closing the most effective channels by which independent researchers, whistle-blowers, cutting-edge laboratories, etc can communicate with the masses. At the individual company level, limiting potential damage is the rational thing to do. There is no easy answer, I suspect.