Comparing coordinates of a known point between the design model and a Print Preparation model shows different values. This is due to the design or map model showing design coordinates (or geographic coordinates) while the Print Prep model shows the same location on the sheet. 

The following describes two workarounds:

Method 1 - Define an ACS to match the design or map model

In this example, an ACS to match the design model is created and set as the active ACS for readout purposes.  To do that, open the ACS dialog, and select Define ACS (Aligned by Reference), followed by a datapoint on the attached design or map model.

The Origin X and Orign Y coordinates will update.

Then copy the modified ACS and rename accordingly.

To use this ACS for displaying coordinates in the status bar, ensure that ACS Position has been selected:

The coordinates now display correctly and as expected.

Method 2 - Place labels using Map Model coordinates

An alternate workflow to display geographic coordinates in the Print Prep model, is by using the  Place Coordinate for Viewport tool from the Print Preparation task.

When used, this tool places the geographic coordinates on your cursor using the active text settings with the Text Style named Coordinates.  You can use this tool to spot check coordinates, or enter a data point to place labels in the Print Prep model.