What is the electrical principle behind LightKeeper Pro?

I saw an ad on TV for LightKeeper Pro today. LightKeeper Pro apparently is a tool that allows the user to fix broken Christmas Tree light strings. Here, you can watch how it works: https://lightkeeperpro.com/instructional-videos/ You'll notice that the way it works is that you unplug a bulb (any bulb) from your broken/one-bulb shorted set. You plug in your set to Wall AC. Then you plug in LightKeeper Pro into the socket for the bulb you just removed. You pull the trigger (up to 30 times), now the lights come on (with the broken bulb showing itself because it's not on). How is this working? You see, in Electrical Engineering 101, if you've got a short in the circuit (which you do if your in-series set of Christmas Tree lights is not working), then the whole set shouldn't work. What LightKeeper Pro seems to do then (I'm guessing), is to use a High-Voltage pulse to somehow get current to conduct THROUGH the non-functioning light. The non-functioning light is, after all (in addition to being an incandescent bulb) a Vacuum Tube, and in theory, if you put enough High Voltage through the Vacuum Tube, it will conduct current through it... is that's what's happening here? Is that the secret? If it is, then I don't really have a question -- problem solved... although it's pretty damning evidence that Electrical Engineering 101 / Electronics 101 -- both books and courses -- are well, sort of wrong with what they're saying about short circuits...