The Scions That Did Not Return

[Thighland]

I don't think this is canon

[UndyingHero]

It isn't canon per se and I don't claim it to be, as I'm extrapolating, but I think it is a reasonable interpretation.
Thanks for your concern and your time friend!
I see nothing gets past your eye.

Soul and memory were transfered, that is implied AND stated.
No mention of consciousness as far as I am aware.
Urianger AND Y'shtola both speak of the risk of "not being the same".
The exarch is alive and conscious when he dies on the first, turning to crystal after the transfer.
The scions are using the exact same tech.
Therefore, the same must happen to them, just as the exarch crystal revives and merges with G'raha's mind, soul and memory, their memory and soul merges with their body, soul and memory, but their conscious mind wasn't there anymore.
Same memory and soul, different brand new mind that is exactly equivalent in all aspects.

cheers!

[Iscah]

The exarch is alive and conscious when he dies on the first, turning to crystal after the transfer.

You seem to be confusing cause and effect. He's already turning to crystal.

His soul is able to escape that body because the spirit vessel is waiting. We can see that the auracite component – the container for the soul – begins to glow at that moment. If there is any kind of "semblance of a person without the original soul" going on, then it's what remains in the Exarch's body once that soul has departed: something like an Endless perhaps; body and memories.

Souls are a tangible science in this story's universe.