In the OP, there is no mention of a WTC and no view of a PCB, so, really, it is just two random pictures without any explanation other than the title saying that it is a "neat trick".
I've been using sticky plastic tape to wrap PCBs and battery packs and provide a water barrier* for the last twenty years, so the novelty escaped me along with everybody else.
* the stuff on larger rolls also makes good deck patches for yachts, as does Duct tape (sometimes "Duck Tape", sometimes "Gaffer of Gaffa Tape)