In the Japanese version of the FF games, Paladin was just called Knight.
In this game, they are royal guards so thinking of them as knights is more fitting, not necessarily holy crusaders.
The idea of Paladin's being "holy knights" and such did not start with DnD but is actually a part of what a "Paladin" is.
The Paladin were the inner circle, or royal guard, for the Holy Roman Emperor Charlemagne, who was integral to the spread of Christianity across Europe. Their name comes from this. The area of a castle/medieval town where the palace and nobility resided was known as the Palatine. The Paladin were known as the knights of the Palatine or Paladine, which has evolved into Paladin. So the royal and holy associations with Paladin are actually a defining factor of the Paladin.
The modern idea of what Paladin are, and where DnD got much of it's concept of Paladin is from Arthurian legend and the Knights of the Round table.
So, yeah ... pre-DnD.
Anyways, with the new post 50 abilities, it seems SE is indeed adding more to PLD to give it that holy Knight tonality.