You both are saying almost the same thing...
The disconnect allows the axle to move better across uneven terrain, or flex. By keeping all 4 tires on the ground you usually have better traction/stability. The downfall of that flex is there is less force applied to the axle, because of the disconnected the sway bar, so a tire can still be on the ground but with a lot less weight on it and just spinning with no traction. BUT to keep connected a limit flex you could end up doing a 3 wheel and now you have a free spin tire in the air, still without traction.... This is all in theory and now my head hurts </BEER/>