I guess they are concerned about shrinkage, but I would want them all to be shrunk so they wouldn't shrink later in uneven amounts (yes, your quilting might not allow as much, but I've seen seams tear away before).
I wash everything FQ and larger. If it shrinks a bit, I try to have plenty of material (so I generally buy a little more than I need).
Plus with Batiks I am always concerned about colors running....