It's weird, but seems natural when you have been randomising 2-12 every turn. 2-12 means there are eleven possible outcomes, two of them being 6 and 9. Therefore you have 2/11 chance of getting a Devil's Eye number.
It's one of those really weird things that looks completely counterintuitive, but that's the way it is.
Of course, with actual real dice the chances of getting a six are higher than those of getting a 12 (more combos deliver it), but that's not the way we've been rolling. Actually... not really as they are independent events. If you roll a 2 the chances that the next dice will be a 4 are the same as those for a second six.