I agree. It is the only time I do pre-wash is my flannel. Since I don't have a washer/dryer any longer, I asked a friend to pre-wash a quilting backing.

I am not a prewasher but I do wash flannel (especially when it is a flannel back to a cotton top). I have had expensive brand name pieces from the same line shrink differently so even if the top is all flannel I would probably prewash.

I never prewash flannel whether it has a cotton top or is all flannel. I've never had any problem after they were washed, but then again, I like that crinkly look. Also, it just seems to me that once they're quilted, it stabilizes the fabric.