Oh. My. Goodness.
I read that part focusing on Ym's interaction with the urchin, and why or how this might cheer the kid up. Paying closer attention, I can see how this actually applies to a few other things.
This sounds suspiciously like what happened to Adonalsium, and perhaps, a few other shards as well. Not necessarily the reasoning behind the shattering, but the fact that it did.
I've read several references to, and postulations of, the Iriali people having migrated to Roshar from other planets. The theory is that they're world hoppers? Or, so I seem to have inferred. So, would this be the fourth world they've come to? Or, perhaps the 2nd physical world, and they are counting the other 2 realms as well?