Exactery! Besides which, who cooks burgers in an oven
There's also a layer of rock in between the gas flames and the metal plates, sorta helps.
But yeah ideally it'd be over a proper charcoal bbq - got introduced to those when some guys from Brazil came over and lived with me for a couple years. Hugely better taste, not because the other one tastes like gas or anything, but because the charcoal ones get extra good smokey flavour that the gas one doesn't.
I personally prefer a cleaner gas cooked burger than a charcoal flavored burger. I can never get the taste of burnt rock and starting fluid out of my mouth.