Why would it matter if the wonder under holds the applique in place once you sew it down? Won't the stitching hold it in place, thus you do not NEED any fusible? as long as you ysed a quality fabric that is not going to fall apart then your applique shouldn't either!

you still have to stitch your applique pieces when using fusable unless it is a wall hanging which will not be washed at all. and if you took a cotton quilt to a dry cleaners for cleaning they would wash it!
as long as you stitch your appliques down they will hold up just fine. fusable is only a tool to hold the peices in place so you can stitch them down. there are some that are permenent bonds that do not need stitching; those are very strong, stiff and about impossible to stitch through...by machine or hand.

If you didn't prewash your fabric or did and used fabric softner that could also be the problem. Next time, prewash and don't use fabric softner.

I was told not even fabric dyer sheets