I don't eat much bread anymore, and even if I did eat bread in sandwiches, I'm not sure I'd think this technique was the greatest thing since .... well, never mind [via Jack].
The argument behind the technique is that toast for sandwiches would be ideal if only it were crisp on the outside of the sandwich and soft on the inside of the sandwich. I don't see that, but if you do, you might want to try this technique.
With most toasters, the slots are quite wide now to accommodate thick items like bagels, crumpets, English muffins, etc. So if you want a sandwich with bread that is crisp on one side and soft on the other side, put two slices in one slot, like this:
Seems like a good idea.... if that's what you really want.
Addendum: Marilyn just noted on FB that most toasters with wide slots also have a bagel setting that toasts only one side.... if that's what your really want.