Nissan changed it so the compressor doesn't shut off even after you de-select a (full or partial) defog setting because the windows rapidly fog up heavily as the moisture that had condensed on the evaporator is released into the cabin as the evaporator warms up again.
Same as the change made for the 2003 models.
http://www.nissan-techinfo.com/nissan/TSB/Feb/54301.asp

The 2000-2004 models also had a problem with the air being warmed somewhat in a non-AC vent mode. The fix for the early models that were especially bad about it was to drill out the holes in the cowl, or get the cowl replaced with a less restrictive version:
http://www.nissan-techinfo.com/nissan/TSB/Feb/53899.asp