(Spoilers)So did the Scions see it?

[Eloah]

My guess is, for the Scion's at least, is they didn't awaken to the Echo because it wasn't really them. As for Ryne, I don't know about her. I don't think she has the Echo, at least the way Minfilia did, but she does have something, being the Oracle of Light and all.

Eden spoiler

In E8 Ryne becomes the vessel for Shiva, similar to Ysayle. However, unlike Ysayle she loses control of herself. Originally, possession of the Echo was thought to be the reason for Ysayle's maintained control. However, it was proven that the summoning of a Primal into one's self does not mean they lose control, as both Thordan and Yotsuyu still retained their sense of being. But Ryne is not as experienced in life as the other three individuals, so that is probably the main reason.

[Jandor]

Eden spoiler

In E8 Ryne becomes the vessel for Shiva, similar to Ysayle. However, unlike Ysayle she loses control of herself. Originally, possession of the Echo was thought to be the reason for Ysayle's maintained control. However, it was proven that the summoning of a Primal into one's self does not mean they lose control, as both Thordan and Yotsuyu still retained their sense of being. But Ryne is not as experienced in life as the other three individuals, so that is probably the main reason.

10 characters:

Did Thordan and Yotsuyu keep control though? The goals of what they summoned were so close to their own that I doubt we'd notice either way?

[TheMightyMollusk]

10 characters:

Did Thordan and Yotsuyu keep control though? The goals of what they summoned were so close to their own that I doubt we'd notice either way?

Ten chars....

Thordan kept control, but Yotsuyu was implied to have lost control after the add phase of the fight. The key difference is that Thordan was completely focused on his goals, while Yotsuyu was conflicted after the specter of Gosetsu showed up among her subconscious ghosts to protect her, which broke her focus and let the primal Tsukuyomi take over.