With the Soulcasting Jasnah uses, the effects are extremely powerful, but also extremely difficult.
With this, Shallan may say, hey, everyone is covered in solid investiture.
And then on on greater levels this could create an explosion due to the displacement of the air. How much acceleration do the air particles have? A heck of a lot, since one moment they’re there, and the other, they are, say, 20 feet away. They would be moving at a substantial fraction of c.
This has already been seen on some level with the density changes due to Soulcasting. When Jasnah soul cast a large boulder into smoke, the smoke expanded outwards.
This wouldn’t do anything much in shadesmar because the general populace doesn’t know much of physics near Roshar.