Actually that statement was 100% accurate.
Doubling down on ignorance is a bad idea.
This is a Faraday cage. It was discovered in 1836, and is rather well understood at this point.
Here's a product you can buy today that completely shields any device inside from any sort of radio signal.
The Silent Pocket® Suit Pocket is a privacy and security case for your phone or electronic device. By putting your device inside you are blocking ALL radio frequency (RF) signal transmissions. This includes blocking all signals from Cellular, GPS, WiFi, Bluetooth, RFID, NFC, etc. This does not harm your device and renders you completely out of service.Don't bother to thank me, I'm happy to educate you. :-)Once inside a Silent Pocket® case you are unhackable, undetectable, and untraceable.