Did you want the bookmatched look?

It’s fine for bookmatched, but that seam could have been tighter.

Yes it is book matched

On second look, they may have "orange peeled" the finish at the seam when polishing.

" Many polishing powders contain a compound known as oxalic acid, which is used to speed the polishing process, and if too much powder is used, the stone can burn. A burned floor has a characteristic dimpled appearance; the stone will have a molten, plastic shine. This burned appearance is commonly called “orange peel,” for reasons that are obvious to anyone who sees it. If the craftsmen orange-peels the floor, he will have to re-hone the floor to remove it. On the other hand, if too little powder is used, the final polish may not be achieved."

Diamond Brite Polishing

lwo, Fred Hueston disagrees with you.

Sorry, you're going to have to Google Slippery Rock Gazette,

How to Polish Difficult Marbles, Part 1 of 2

I've got MB12 in my restoration bag of tricks. It's got oxalic acid in it and it works great.