Mmmm the yoshinkan was stablish way before iwama. I think the similarities you find are because both Shioda sensei and Saito sensei were direct students of Ueshiba sensei and both keep it traditional and faithful to what they learned. Shioda sensei was senpai of Saito sensei nonetheless he will send students to learn with him to expand the horizon of his students since Saito sensei was closer to the Ueshiba sensei at the end