Interesting, they clearly do have an effect, as I suspected. In everyday use, I still wouldn't worry about it, though. Crucially, the signal strength drops massively with distance, so it doesn't take much to reduce it
I appreciated how he pointed out that this wasn't a scientifically controlled test accounting for all confounding factors, but the results still mean something.
I also watched a handful of other videos on that channel. Bite sized and full of good info, I've subbed this channel.