The theft techniques discussed above relate to the kind of keyless entry where you don't need to touch the fob to unlock the door.
The key to understanding this is that a car with that system emits a constant signal. "Constant" is just that--all the time. If you keep that in mind when walking through the example in the above post you see how the thieves are pirating the car's constant signal, using it to wake up the fob, and then pirating the fobs response signal to unlock the door and presumably start the car.
It would be simpler if it was the fob that emitted the constant signal, not the car. But then you'd be constantly replacing the fob battery. That would also eliminate a a couple of steps for thieves.
If you bought a new car today in the US you'd probably have a hard time finding one that doesn't come with a "touchless" fob. Maybe a low trim entry level vehicle. It is standard on CX-5, for example, from at least Touring on up, maybe in Sport too, I don't know. That's in the US anyway.
Personally, I see no need to take any precautions such as keeping the fob in a metal box. Other's circumstances may vary. Obviously, this theft technique is pretty much limited to cars parked in driveways, the low hanging fruit. They're not going to mess with breaking into garages. If you park on a street with houses they would have to guess which residence has the fob; that involves trial and error when time is of the essence. They'll skip that one. If you live in an apartment building or while you are at work? Fuggetaboutit. They have no idea where the fob is and probably couldn't get close enough to it anyway regardless.
These kinds of sophisticated thieves are opportunists and that means cars in driveways as the prime targets.