Well, there are more Iwama lineage than Saito Hitohiro.
Yes, I know what you mean. But that's not the impression you get when you listen to Hitohiro talk. The lineage is presented as a straight line: Morihei-Morihiro-Hitohiro, with no allowance for variation or changes along the way. And no mention of other senior students at Iwama like Inagaki or Isoyama.