How would keeping the key in a blocking pouch help? I thought they were implying this was done without any reference to the keys
No it requires a keyless keyfob to be in the vicinity.
This attack involves 1 guy using some sort of device that acts as an antenna and booster. He walks around the house, as the other guy constantly tries to open the door. The act of the guy trying the doorhandle gets the car to 'ping' for a nearby keyless entry key. Many keys are clearly left close enough to widows/doors etc, that if you are just outside the house, the signal can be picked up. Using an amplifier boosts this. I imagine it is boosting the return signal from the key rather than the signal from the car, or maybe both.
Once the door is opened, he is in and he constantly tries to start the car, which again results in a 'ping' for a keyless key each time. Once started, they are away. Both cars that I've had which are keyless allow the car to run when the key is out of range, it just sounds a bell to say the key isn't in range anymore. So as long as the car is started, they can drive it until it runs out of fuel.
The pouches onsale act as a faraday cage, stopping the 'ping' from the car reach the key. So whereever you normally keep you key, you just leave the pouch there and put the key in at night and lift it out in the morning.
Here is the video. of the one I saw (it was originaly posted on another thread)
https://www.youtube.com/watch?v=Ti79UhY0TGc
It's not entirely clear the exact procedure in this video, but I think in this instance, once the car was unlocked, he stayed outside the car and pressed the brake pedal with a sitck and kept pressing the start button, whilst his mate used the antenna. If caught before the car started, it was a quicker get-away than if seated in the car.