They are also frequency-hopping, meaning they constantly switch what part of the band they use, and there are a few rc radio protocols use a dual frequency system for redundancy. FRsky has one that does 2.4Ghz and 900Mhz at the same time.

So to make sure you are jamming all (commercial) drones, you need to deafen everything from ~850Mhz up to 5.9Ghz.