DC pass on one port is included so that a customer can install the splitter in a "where needed" location instead of being restricted to installing it at the output of the power inserter. We have several diagrams on our web site that show various configurations of amplifiers and splitters. See
http://www.antennasdirect.com/empoweren10475.html for the menu.
If you don't need to make use of that feature, then it can be ignored.