This looks like someone told the contractor that it would be $15-17 a square foot to install and they said “I’ve driven past a Taco Bell before, I can do that myself”. The thing is even Taco Bell puts mortar between the joints of a bonded stone (even though they don’t bond them). This is not only terrible looking work, it’s installed incorrectly, and as someone already pointed out, that stone under the vent was installed, but has already failed due to improper installation, and only a portent of things to come.