I was asked to inspect this job today and was told by the home owners that the installer when questioned about the uneven finish, that it was the best anyone could do.
The floor wasn't properly leveled and ... get ready ..... he used a 1/2" x 1/2" square notched trowel.

Note the space between the tile and the center and right end of the level. There is almost 1/2" difference in a span of 12".