I saw this listed in the advertised specs for these two cards too, and I wondered what they meant by it. My guess is that they are comparing using the card to the old version of Flashme, before Flashme used the DSL firmware (so you couldn't change the brightness). Of course now Flashme has been updated you can change the DSL brightness, but I'm guessing they haven't updated the MK4 advertising yet.
If anyone knows any different, please post.