It's not just the "color". The technology to create those finishes is itself extremely complex and difficult to accomplish. One of the things many people like about Apple products is the company's (or Jony Ive's) obsession with producing hardware that looks and also feels good, solid, pleasing. Some people find those details silly and pointless but lots of people appreciate meticulously crafted objects. Gruber is definitely that sort of person, and he writes for that sort of person. You may judge the relative value of other aspects of the device differently but I think it's reasonable that many phone buyers would be deeply concerned about the look and feel of a device they carry with them everywhere they go and use and touch more than literally any other object in their life.
I don't know, I think Apple makes good hardware but I doubt they needed such complex technology to create shiny metal. The video describing the process made it seem more about marketing checkboxes than actual improvements.
