I can't say for sure if they've always specialized in Masai, I'll have to go back through some of my old issues of ZooView magazine to check. But they have displayed Masai for many, many years now.
If I remember correctly, I'm almost positive that sometime during the 1970s, L.A. did exhibit the Angolan or Smoky subspecies for a time. Maybe even from its very opening in 1966.
Just a thought on what they once exhibited. I'll continue searching through my older zoo publications which go all the way back to their opening in 1966. I could be wrong.
And here is an article from 1984, that confirms that not only did they exhibit Angolan Giraffes at one time, they were also successfully bred here. The article is in reference to the once existing herd at the Baltimore Zoo, and a then recent birth there from parents of a wild caught father, and a female born at the Los Angeles Zoo.