it depends on how the parking pawl is engaged in the trans as you say. the center diff int he 5eat is a planetary gear set i think, not a regular ring and pinion with carrier and spider gears. its possible that though the pawl is engages in the trans, it may need to have both outputs of the center diff to move to move the section that has the pawl. if the pawl is only on one of the center diff outputs, then the other output would be free to spin with all the clutch packs disengaged int he trans.
I am not certain on this. logic would assume that the pawl would engage before the the center diff, and that should lock it if the other output is locks by the front wheels being on the ground.
4-Time NNJR ESP Season Champion -15 ESP
3rd Place in 09' Pax Championship/Driver of the Year
2012 Northeast Divisional Champion in ESP