You are all missing the obvious.
In context, the RC is a powerful transmitter. The signal level of the distant Mavic compared to the transmit power of an RC right next to you is several orders of magnitude.
I would be surprised if another RC within a few feet wouldn't present a strong interference signal. It has nothing to do with the modulation techniques (
@Thunderdrones is right -- current modern transmission and modulation techniques make channel conflict a thing of the past).
It has to do with, by analogy, someone shouting with a megaphone right next to you when you're trying to hear a very quiet shout from 300 yards away.
ANY transmitter within a few feet transmitting on 2.4Ghz at the same EIRP as the RC will cause the same interference. People need to simply keep an appropriate separation when flying together, probably no more than 10-20 feet being necessary.