We SAW T'Lar. In fact, it might even be argued that the officials who oversaw Spock's Kohlinar ritual in The Motion Picture were some sort of priests/priestesses. Until that movie, we hadn't seen any more of Vulcan than what was seen in Amok Time and Yesteryear. And not one frame of it included anything remotely resembling royalty.
I saw the Kohlinar masters as teachers. T'lar could be a teacher, scholar or physician. She was never addressed as a religious leader in the film. Anytime we're given new information about Vulcan it's a first. There is an entire litany of firsts for Vulcans. None of which we had ever seen or heard of, until we did. I don't see why this is different than Pon Farr, inner eyelids, mind melds or Kohlinar.