I think this means that the phone is equipped with antennas for different "LTE/4G" frequencies. This makes the phone work with different carriers throughout the world. The second antenna is for compatibility.

It's unlikely that the phone will spend power activating antennas that are not in use given the carrier/geographic standard, so my best guess is this: No. You will not see double the radiation.

(I could be completely wrong here, though. I'm not a cellular engineer by any standard.)