Think of an RFID chip like a tiny mirror with a message written on it. If you hit it with a signal on the wavelength it was made to work with, the signal bounces back to you and you can read the message.

Sure, you could use 5g, but RFID chips typically carry a very small amount of data; the proposed Gates 666 chips would only really need to hold an ID number that they can look up in a database to find the rest of your info, like those chips you can get implanted in your pet to find them if they run away.

The main advantage of 5g is that it can carry a large amount of data, so that would just be a waste of money for something that only needs to hold an ID#. Especially if you wanted to scan a crowd, you'd want something longer ranged.