Sure it's possible they came from the same slab.

Not lot to do about it now, if you were as concerned about the look/layout as you sound you should have gone to the shop and approved the layout before cutting.

a lot has to do with slab yield and how the pieces are cut and how they are spliced. When the grain continues in the same direction things are usually fine, when it changes direction (often at a 90 deg. corner) things can get dicey.

You might enquire about paying for another slab from the same lot/batch and see if they'll comp the labor to splice in a new piece or redo the entire run.

I'm sure there was language in the deal about "natural" material and variations ect... that are not defects. What you have is buyer's remorse because it's not how you envisioned - which is often impossible.

Good point about viewing the layout before cutting. I didn't think the background would change color that drastically due to change in grain direction. The other two pieces are EXACTLY the same background color even though the grain is rotated 90 degrees. This is what made me wonder whether that one piece could have been from a different slab even though I bought a single slab and viewed it before layout or cutting.