RF energy is strange stuff. The coupling to your hand will change its radiation pattern and reception sensitivity. For any phone, where you put your hand changes its RF abilities. The engineers try to make it so common hand holds aren't too bad.
If you are old enough to remember analog TV and "rabbit ears" then you might remember the frustration of trying to adjust your rabbit ears to get good reception on a station. Sometimes it would be great while you were standing near the antenna, but bad when you walked away. Sometimes people would resort to distorting the patterns directly with aluminum foil tags on the rabbit ears.
The same thing happens to phones, though the distances are much smaller because of the frequencies.
If you want to experiment, remember that the direction to the current tower is also important in this system. There is no reason to believe your phone receives uniformly well in a polar pattern about your vertical axis.
Go someplace with less than full bars. Get a grip. Turn 360 degrees slowly enough for the bars to respond, record data at various angles. Try a different grip. Repeat.
Yes, I get that stuff. Now how does attaching a bit of tape over the gap, or avoiding bridging the gap with your hand play into that?
It's like they're saying "yes this is a common problem in phones that we're well aware of and which our unique new "genius" design makes worse" without wanting to actually admit the latter bit. So you end up with strange-double talk advice that tells you how to fix problems they're not admitting to having.
Most importantly for the meme, that little gap in the metal provides a focal point for people to stare at and say Well there's your problem! It isn't nearly as interesting as "hand vaguely cupped about the lower third with the pinky extended and then curled back touching the bottom left side while up against my face" (which is the transmission killer on my first generation iPhone. If our connection breaks up, there is no reason to assume it was an accident.)
It seems likely that plain old electrical conductivity is in play here. Some people's skin conducts much better than others and anecdotally tape insulation helps. So that is a different mechanism from most(all?) other phones.
If you are old enough to remember analog TV and "rabbit ears" then you might remember the frustration of trying to adjust your rabbit ears to get good reception on a station. Sometimes it would be great while you were standing near the antenna, but bad when you walked away. Sometimes people would resort to distorting the patterns directly with aluminum foil tags on the rabbit ears.
The same thing happens to phones, though the distances are much smaller because of the frequencies.
If you want to experiment, remember that the direction to the current tower is also important in this system. There is no reason to believe your phone receives uniformly well in a polar pattern about your vertical axis.
Go someplace with less than full bars. Get a grip. Turn 360 degrees slowly enough for the bars to respond, record data at various angles. Try a different grip. Repeat.