>> So they don’t effectively block communication to and from the device?

> That is impossible to know without knowing the characteristics of the signal

Do you dispute that de facto these products work?

Yes I have spent thousands of dollars and months testing them.

You can cut off GPS and high frequency cell spectrum pretty easily. Most cell spectrum is effectively attenuated by good quality professional RF enclosures designed for those frequencies. 2.4 ghz signals like wifi (with good quality radios) are hard to attenuate to the point where they can’t connect to other radios nearby, even with very expensive RF test enclosures.

If you’re trying to block against an unknown threat you are fucked. If someone wanted to back door a baseband they’d probably make it transmit at low speeds and low frequencies to be resistant to attenuation.

I will, I've got two and neither one can shut off a longwave FM radio.