That's not how this works.
Having played with quite a few wireless transmitters, homemade even, for electrical engineering, the hands are basically creating a faraday cage, with the hand absorbing nearly all the waves, leaving nothing out.
If there's enough surface for the wave to find a way out, it'll likely find it's way to the switch unit (given non crazy distances).
A person walking in front of you is not going to cover the joycon, the wireless signal will not stop, there's so many of them it'll find the unit. Imagine a wireless world with your proposition for a moment, it'd be completely useless.
I'll repeat, if there is a problem, don't show me someone covering the whole thing, ask that guy that first reported so many problems. It can happen, there can be problems with hardware. That gamexplain video is something else, i mean cmon, it's the equivalent of what happens if i put a dualshock4 or a wiimote up my ass? Will it work? Let's find out!