Mc command center not changing elders ages?

Well, the main difference is that for adults and younger, the aging bar shows how many days this sim has left until birthday, while for elders and sims who don't age, it shows how many days have they lived (literally so it increases every day even when aging is off).
So the number that is shown for elders doesn't matter. What matters is how much their aging bar has filled up. When elder is close to death by old age, you'll get notifications telling you that.