It sounds like its more voltage, but what's really happening is that instead of 120v hot on one leg and return on the other leg, with 240v you have 120v hot on each leg of the outlet.
If the input is designed to work with or accommodate 2 120v legs - and whatever switching transformer/circuitry can work with both legs hot, then it's probably OK.
Not that I would try this, but if people are saying it works I get it and it is interesting to me academically.
From a practical standpoint, its above the level of risk I am personally comfortable with.