Remember when we used to dampen our cloths and bag them in the refrigerator? It is suppose to release wrinkles. You could try it. I like to put some vinegar right in my iron with the water to steam material.
My best guest about rippling is that if you are dampening only part of the unwashed fabric, it might be shrinking and you are relaxing only part of the fabric. The un dampened part is still stiff with sizing.
Why don't you just wash the stuff and be done with the problem. Iron it while still damp or dry it and hand press and fold and put in stash. I don't press fabric until I am ready to use it, and I only press the amount I want for a project, the remaining fabric goes back into the stash for the next project. There are several good reasons to wash fabric before using it.
shrinking
bleeding colors
removing chemicals you really don't want to have in the fabric
for me the most important thing about washing fabric is to see how it will act in a quilt. Fabrics are different quality and react to washing and show you how well they will work.
I have washed what I thought was wonderful fabric and it came out so wrinkled and pill'd I couldn't use it. Some will fray so bad you won't want to use it. Some get rough with washing. some fade so bad they are a different color.
Washing may be step we don't like but really, it is a simple task. We don't have to beat the fabric with a rock in a stream. It also saves $ on those color catchers that seem so popular.
It also saves on heart ache when an unwashed project goes bad, know what I mean!
Just sayin'.
peace