Yeah, I agree, if that is your complaint, I would stop comp[laining. It will be worse than that if a few months just from seasonal movements that no one will be able to stop, help or fix.

"To me it's as if the circular saw blade was blunt. It was dry cut on site. And there are some which have been cut straight."

I'm not understanding your complaint. The work looks fine to me.

Post a picture that is taken from twelve feet away from the seam.

It looks chewed by beavers. Not just the execution is poor. The overall design is poor, without enough expansion gaps used. With zero mechanical fastening involved, and only thinset, if the substrate to that is wood, you will have all kinds of major issues down the road. If it's metal. Same. Expansion rates are too different. Only a steel reinforced concrete substrate would be close enough to having similar expansion coefficient. Mechanically fastening would still be advisable for any "floating" installation. With the industry required expansion gaps. Or it may cease to float and fall on someone's head.

Did you seriously apply moarble over wood? And no railings???

If you're in the states and those treads are less than 11" deep, you don't have the code-required nosing over the risers.

Update: Thank you all for your input. The stairs are not wood but concrete base. We are based in europe. The marble heads have been attached by using mortar, glue and pins. Some are cut straight with no issues and others as shown in pic do look like the cuts were done with a blunt blade (as seen in pics). The stairs have also just recently been finished and each head (where there is a seam it's were it's been cut and grouted.) The railing will eventually be secured to the sides too (currently being manufactured). It's driving me insane knowing that some have been cut fine and others haven't. I've spoken with the installer who is blaming the marble chosen saying it's a "softer" stone. The factory knew we were choosing marble for the stairs. Would you go back to them and complain?.

" Would you go back to them and complain?. "

Did you read the replies above?

"Europe" ?? You should seek advice locally.