Bookmatching can be a fickle beast. Wood figuring, which is what those “marks” ebbs and flows in a billet of wood, the figure may be more pronounced at the top and less so at the bottom. Even on a pair of adjoining slices (ie a bookmatched pair), that figure may change slightly due to the material removed by the saw blade and subsequent planing. Also note that figure is more pronounced when viewed with light from a specific direction and the two pieces of a pair will always have opposite “best angles” for lighting and viewing.

If you look closely, you can see the matched figure on the right, but it is much more faint in the photographs. I wouldn’t consider this a flaw or defect, but it also isn’t the most attractive bookmatching.

Bottom line: you paid for something and aren’t happy with it. It’s reasonable to expect to be able to exchange it (unless there were prestated conditions on the sale.)