I have no problem with Capaldi being 14 and have David Tennant using up a regen even though he remained the same doctor. He used up just as much energy as he would have used if he had changed, and that is explained at the time. Just because he didn't change doesn't mean the cycle didn't get bumped. I have have no problem with the way he got a new set of regenerations, this is not the first time that the Time Lords gave out more.