Each tile will have different levels of porosity... the shiny parts are dried on sealer that should have been buffed off... the stripes IMO are residue from the packer skips between each tile and a wash with grimex would have sorted that...
I agree with Dave on all accounts. It has to be some residue or etching caused by the packing vs moisture must have effected the stone and there is way excess sealer in places.
Yes, that needs a floor refinisher to fix unless you own the tools. If I was there I would use a fine and very fine grit wood floor sanding screen with a white pad on a swing machine (mono 175 rpm) or diamonds (200-600 grit) to do a light grind in place. Then 5x powder polish. Have this done after the grout is installed because if the joints are filled full the process will make the floor very smooth and easy to care for later.