Well they could use a flash drive that doesn’t mean it’s a good idea. Flash memory has limited read/write cycles and if you are continuously using the drive/stick/whatever it will start losing data and getting errors. Also they are ssssllllooooooooowwwwwwwwwwwww.
A better (but a bit more expensive) alternative would be a small external USB 3 drive that takes its power from the usb port.