I clicked on the link and thought the same thing. If its wires to the incoming power then its basically a surge protector/suppressor as those work the same way, they shunt over voltage to ground. Usually surge protectors/suppressors use MOV's and there are varying levels of quality of speed of response. So I'd speculate for the price its hopefully a high quality surge suppressor/protector.

What used to get people a lot was not the EMP/EMF through the power grid as most electric devices are tolerant of some fluctuation of voltage and surges/spikes/etc but rather a surge through another entry into the home like a phone or cable line or tv antenna. My pc repair days we found many a blown up modem and many of those people upset because they had a surge protector/suppressor. Lightning would strike the pole or near the lines between the poles and the surge would come in the power and phone line and the surge suppressor would shunt the power but the directly connected modem would still get the hit from the surge on the phone line.

So this device is kind of like putting an expensive lock on the front door while leaving the back door open. You need to protect any and all other wires coming into the home. Also it would do nothing for non-grid connected devices hit by a local EMP that wasn't traveling through the power lines.

Most of us now a days will change internet/cable/phone providers somewhat often as we get better deals and technology changes. One thing I've always done is followed any wire I'm not using to the outside box and disconnect it there to isolate that connection from the rest of the grid.