Designing Kitchens and Bathrooms - Wicking on granite shower wall

I recently had a neo-angle shower installed with an acrylic shower base. The two walls are natural granite. After using the shower, I noticed one of the walls is "stained" by wicking of water somehow. It is ugly, and I am wondering why this is happening. The opposite wall (that gets just as wet) does not do this. If I don't use the shower for 2 or 3 days, it disappears. The installer claims granite is porous and this is a natural thing. He seems to have no solution and said he'd consult the "marble institute." I think I'm getting the runaround and that it was properly installed. The wicking occurs where the granite meets the acrylic.
Any thoughts?

Granite is indeed porous and it will absorb water along with lots of other things. Water stains will usually disappear after a couple of days, some other stains need to be treated to be removed.

Your installer should have sealed the granite. You can get a granite sealer at any home center. Wait for the water stains to disappear and seal the granite according to the mfrs instructions.

Some granites are more porous than others, and some will take more sealer than others. So yes the answer may be to seal the granite.

The wicking occurs where the granite meets the acrylic.

Was the joint where the granite meets the base properly caulked? Also curious, how were these granite panels installed?