Same thing happened to me. Could it be that the fabric company is trying to squeeze out every inch of fabric to make a buck? I think they cut those (jelly roll) strips first and then use the rest for the "fat quarter". Just an idea I had.
I purchased a package of 20 coordinating fat quarters from JoAnn's a while back--waited until they were on sale. I was planning to make a Turning Twenty quilt. I ironed each one and then went to cut. They were much smaller than what a regular fat quarter should measure. Thank goodness the Turning Twenty quilt had instructions "in case" the measurements were different. I think the author must have had the same experience.