As soon as I read 'poplin' ridges came to mind. But this is from probably 40 years ago. So I went to Wikipedia to refresh my memory. It is an even weave that can be made from a variety of materials but did in the past often have ribbing. I have not seen any for years. As an even weave it could be the same as any other quilting cotton but can have ribs or ridges. To me this is the difficulty of a website. I want to feel the fabric before I buy. Are you a gambler? If it turns out to be thin or you don't like it what would you do with it?
OOps it sounds like you already bought some.