Is there some new regulation or policy that removes your promotable status when you are nearing ETS?

I graduate BLC at the end of September, and I was expecting to pick up SGT on the 1st of November, but didn't make the list. I checked my PPW and it showed I was ineligible about 7 days before I graduated and the reason was “reenlist”. I don’t ets until February, is there some new reg that removes promotable status when nearing ETS, because I have had soldiers in my unit that have went to blc, promote to SGT and ETS the same month.