The granite was not sufficiently sealed. That color normally takes 4-8 initial applications of sealer. After that you shouldn't have to seal it for 5-10 years.

Thanks kevdp! I suspected as much.

Fortunately, the fabricator seems cooperative and will probably rectify it. Will they need to allow some time in between sealant applications? If so, how much?

Yes. To be most effective there should be 24 hrs between coats.

Thanks again, kevdp.