The width can legitimately vary from as narrow as 20 inches to as wide as 22.5 inches - depending on the width of the fabric.
However, cuts shorter than 18 inches and crooked really tick me off - I don't know any way around it except to open the pack and measure the pieces in the store if one wants to avoid the being upset when one gets home bit.
And that goes over about as well as a floating brown log in a punch bowl!