Originally Posted by
DiaDeem
I believe the conditions to Ardbert's crystal were much more circumstantial/specific than everyone else's. I truly don't think the scene would have happened without the crystal. I believe the crystal, combined with how senstive Amaro are to souls basically allowed the whole thing to happen.
Someone also pointed it out, that even Seto himself upon first meeting the WoL states "Strikingly similar, but you are you". If the soul was different/mixed post merging, I think all Ryne, Shtola and Feo would have pointed that out afterwards, but it is "More dense, yet normal. Restored" somewhat grouping the descriptors we have so far.
I firmly believe that though Azem's soul was once whole, it can never be recreated as it once was, and thus each individual is their own. Even the WoL tells Elidibus right before he turns into his boss form something along the lines of... "Those you wanna bring back are long gone" referring to the Congregation, very much pointing that sundered souls once gone are gone (looking for the actual quote and will edit to the proper one once I find it). That's part of the futility of Elidibus' quest.
There's a bit more on the themes reincarnation and individuality within the Pixies Quests, but I don't want to spoil that if you haven't played them!