I must admit, I've not really had a good look into what is known of Yolen, or really thought through the implications there.
We don't really know why Adonalsium shattered. The assumption is that it was not voluntarily, but is that just inferred with the word 'shattered'? Most things don't spontaneously shatter, but if Adonalsium had some form of sentience? I suppose probably something more like 'split' would have been used if it consciously divided itself.
I would ask the question however, why when it shattered did it form 16 shards of equal power, which, through their individual intent, sorta have a purpose? Or even just, why equal power?
Do we know what happened to Yolen after Adonalsium shattered, and the shards left? Do we know if any shards remained?
I'm curious, cos I'd like to know why the shards left to go throughout the cosmere, opposed to remaining on Yolen.
On a side note, all this would put a different slant on what Hoid is doing, why he's opposing Odium, because Odium would be working to prevent Adonalsium reformed.