It has been along time since I purchased fabric that was a true 45 inch wide... Its not just a Jo Anns issue.
I remember when poly was intoduced and becoming the norm at the fabric store , the most distguishing way to determine fiber content at a glance was quilters cottons /calicos were 36 inch. The bolts were shorter than everything else and almost all fabric was wound on the bolt inside out . They had to flip the ends over the bolt to present the right side to the customer.