CFD Post is the traditional post-processor for the CFX solver. CFX only allows "pseudo" 2D models (one through cell). Because of that, the 2D Fluent results have to be adapted to be read by the 3D CFD Post and that sometimes leads to these weird artifacts.

As for the changing reference depth in Fluent from 1 [m], I would be very careful about doing that. In earlier versions, there were known complications that arose when this was changed off the 1 [m]. Unless you have a reason to change it, leave it alone.