I've only owned one TJ D44 (2001), it did have the 3 ribs, but I don't know if they all do, never bothered looking. The XJ D44s came in two different styles:
Here is one I found in an '89 (not many '89s had them) it has one single thick rib. (and before anyone points it out... yes the pinion angle was wrong in that picture, it was later fixed)
And this one came out of an '87, it has the 3 ribs.
I don't know if there is any strength difference between the two.