with modern batting the chances of migrating through the seams is minimal. most quilters today stitch over and across the seams anyway holding the batting in place.
in years past, battings were looser and came apart and migrated more easily and were more of a problem.
like a lot of questionable practices among quilters,this will never have an answer. like washing before cutting. quilters have to try out each method and see what works best for them and go with it.