I never heard of that method, but it makes sense.

It sounds closer to doing it the traditional way: slow simmering sweetened milk until it turns into a caramel consistency.

I know with the sealed method, some people boil more than one, then put them back on the shelf. So their pantry will have regular condensed milk with the label on, and cans of Dulce de Leche with the label off.

No idea if this is actually safe to do, though. I just know some do it ¯\_(ツ)_/¯