Not sure I agree....
I don't know much and I don't use the KO count, but it was my understanding that is isn't so much that KO assumes that 4 sevens will come out each deck, but it uses the unbalanced nature of the count to determine shoe depth.
I familiar with the Red-7, an unbalanced system that simply counts the red-7's as +1, giving a +2 count per deck. In that system, you simply start your count at -2 per deck, instead of zero. So in a 6D shoe you would start with a count of -12 and only increase your bet when then count hits zero. It is this negative starting place that makes up for the lack of a TC. Rather than being the 7s, it is the assumption that as each deck is dealt, the count will increase by +2. If the count increases more than that, then the remaining deck is positive. Less than that, negative.
It makes sense, but it also seems to me that it wouldn't be as accurate in determining the current deck make-up as a balanced count. However, I don't have math to back that up, just an impression.