According to Nintendo’s official website, “This update provides behind-the-scenes improvements to system performance. So download it and see what so new about it, and will it block flash cards.
After doing some more research on the update, it seems like its just to block out flash cards again. So far Acekard 2i and Supercard DSTwo are in fact blocked, so don't update if you have these cards, and the EZ-Flash Vi and iSmart DS are unblocked.