Your comments above are understood, and yes I agree that this type of product is useful for minimal protection. Yes, it is neat.
All that said, and something that I should have mentioned previously, the described install responsibility for the EC IMHO ends at the receptacle the EC installed, along with the branch circuit and OCP. A 'plug in' item is not within the responsibility of the EC.
BTW, I see no indication of any UL/CSA at the links, but verbage indicating not for use to extend permanent circuits.