It shouldn't go to pieces when soaked, and I think it was the Fairfield 100% cotton batting that worked this way. Maybe the 80/20 can't handle being soaked.
I guess my conclusion is that it would be a lot safer to use Hobbs 80/20! No need to soak, and no problems. It may be more expensive, but with all the work that goes into making a quilt I'd rather be safe than sorry!