This would be funny if so many people wouldn't fall for thinking it means there is any risk of harm. Just don't take it in the tub.

On top of that, I'm pretty sure the video is faked (we can't see his right foot or his entire back) or he has a faulty charging brick. USB and apple charging cords only carry DC power and chicken sticks only detect AC. That is why it doesn't beep for the unplugged phone, phones are all DC internally.

I'll have to do some testing of my own next time I'm home. Not because there is any risk. Because I am a nerd who wants to test his own assumptions about his understanding of how those meters work and how that affects when they go off.