I doubt enough signal reflect of off your very radio wave observing skull to make much of a difference at all, it's most likely a placebo effect and the real reason it extends the range is because you are holding the key fob higher, so it has a better LOS with less obstructions, and it has a better chance to bounce waves off of the very reflective concrete on the ground up to the sensor of your car.

Organic materials are absolute crap at reflecting wireless signals, they are much better at absorbing and scattering them.