Are shards different?

[Lurina]

Back on topic, I don't think the whole "rejoining of the soul" is very well explained in the game and it's painfully obvious it was tacked onto the plot after the fact. Every rejoining doesn't increase your lifespan or else we would have heard about it in records or after the most recent calamity or from the story that leads into the 8UC. You would think that a group of people plus G'raha would have made a comment about any sort of change within them after experiencing 2 calamities but we don't hear of it. We would also have known about it from G'raha and all of the Scions on the First since the people on the First are just 1/14th, but again nothing. But at the same time it's a bit weird that as soon as all the rejoinings are complete, we'd all be "whole" 20ft-tall Ancients again at the same power level. A part of me wonders if it's not that simple and that a lot of that idea is Ascian propaganda fed to Varis in order for him to do what they wanted him to do.

Again, it's not just Varis. Emet spells out the same concept late in ShB.

Remember, you are of the Source. Unlike the halfmen here, you stand only to gain. Should you survive the remaining calamities, you will become our equal. A complete existence in a complete world.

This is during his moment of vulnerability when he almost addresses you as Azem right before you take the elevator in Kholusia, so I doubt they intended him to be talking out of his butt.