this is strange.
By my understanding, when you touch the iphone, your whole body should act like an antennae and boost the signal
Well, you're obviously not an RF engineer. (Nor am I, but I am an ex-licensed amateur radio operator, have built my own equipment, etc.)
When you touch an antenna, you totally screw-up it's RF characteristics. Yes, that's a technical term. "Tuning" a "human antenna" involves a chain saw and limbs. It's not terribly practical.
I don't know WHAT they were thinking. How many RF engineers quit Apple over this bull-headed determination favoring form over function? Jon Ive may be perceived as a great designer, but this is a prime example of elegant design triumphing over usability.
I think this has been a persistent issue at Apple, you can see it in a number of their products - the non-flat back of the iPad is another example of design that doesn't function well. The curved back of older iPhones is much less of a problem than with iPad. You can't type on iPad on a flat surface without it "rocking". And, I'm sorry, but little square keyboard keys with minimal throw are non-optimal. Pretty, but pretty non-functional.
The gap that allows you to bridge the antenna is the most stupid blunder of all.
I suspect that the bumper was their last-minute attempt to paper-over this goof.
Hopefully, the connection from whatever internal antenna there is to this silly doo-dad is made through some sort of electronic switch, so that they can turn this silliness off with firmware and just use the internal antennas.