I was told in a class one time that almost all fabric has sizing on it to make it look and feel thicker, which is why you need to at least rinse your fabric and dry it before ironing on any of the Heat & Bond type products. I would imagine it works the same for the spray on basting products, too. This also explains why sometimes when you wash new fabric that had a nice weight to it before you washed it, comes out of the dryer like a thin, limp noodle.
I've only used the basting spray twice in my life. The first time I used it, I guess I was too generous with it and the little mini-quilt came out so stiff after I basted it, that is could have stood up and walked away. The second time, I was less generous with it and it wouldn't stay together while I was sewing it. I ended up pinning it like I always do. The third time for me should be a charm... if there will be a third time, that is.
Good luck.