I agree about it being one of the least porous materials but even the worktops that are installed in kitchens should be sealed periodically to protect them. I fitted some granite years ago and someone split red wine on it, it would not come out so I always seal first now just in case.
I'm with Tel...do a water test first...some granite when factory finished is pre-sealed..so you don't want to be cross sealing or you will have more trouble..
I'm with Tel...do a water test first...some granite when factory finished is pre-sealed..so you don't want to be cross sealing or you will have more trouble..