In general, BCN will report true compass numbers on the Nav screen. We do not try to compensate for magnetic variation, because the receivers either don't report this number or report it unreliably.

For the Nomad, you will need to activate the VTG sentence in order to get bearing updates as explained on this page:

http://www.backcountrynavigator.com/content/view/80/1/

However, the bearings should be a separate issue from whether you get accurate readings when collecting waypoints.

There may be some more things I can learn about the Nomad by looking at my notes from when I had the demo unit from them. I'll be able to look at that later today.