Why does the 7+ get so hot when dowloading wifi

Anyone else get this? It gets really really hot under wifi and if you run a geekbench while its downloading the scores come in very low or use the two lower processors. If just using wifi why is the processor being taxed just for downloading and writing to flash.

Tried on 6S plus and that is not the case there.

Have a 7+ intel modem. Just dowloaded an itunes movie. It could be an itunes app store issue too- apple allowed them to use the strongest resources in the cpu.