I think this is almost entirely a publicity stunt. It's easy to detect the manufacturer's OUI, and they're already selling a device that examines WiFi traffic, so why not add a signature for the Parrot? It costs them almost nothing, and it's kind of attractive in a faux-nerdy marketing person way. The salesman can use it to joke with the CIO when he's trying to sell them. The engineers will roll their eyes. but the executives will think they're doing something useful.
The real question is if detecting R/C signals is worthwhile. Parrot's WiFi control is only one of many possible protocols they could use on the 2.4 spectrum, and there are many other bands available to R/C owners. If R/C is a real threat, they need to detect them all. Otherwise, their existing software to detect rogue access points is probably more important than identifying specific toys.
Regardless of the technical merit, I think the marketing value is probably more than valuable enough to keep the rule around.