But would it give peace of mind really? Right in the linked video. It would seem the widget is properly designed, it has a thick separation gap between the two

But would it give peace of mind really? Right in the linked video. It would seem the widget is properly designed, it has a thick separation gap between the two sides on the pcb. It would seem, that you could test 10 of these and they are all fine, and the 11th kills you. Or is that transformer design obviously unsafe?