If I'm reading this correctly, this attack requires access to the PC in its initial stage to deploy the malware. I don't think a hacker will use this method to target your everyday crypto users since they need to set up a way to receive the signal emitted from the RAM. Maybe they will use this to target exchanges, whales who publicly say they store crypto in their home, etc. I don't think it's a good idea to use a USB or something similar to transfer data to an air-gapped device to begin with.