Questions about Locking Doors

I just looked in the manual and it does say

the trunk should lock back, depending on whether or not central locking is activated. I activated and no change. My security system doesn't reset either. I think something is not right. I'll do the activate thing again to be certain. Thanks fellas.

I can lock it from any location - inside using the safety mechanism,

inside using the central locking switch (the one on the console) and outside using the keyfob. It all works well. Here's the issue:

1 - Lock using keyfob, security system sets OK.
2 - Now, unlock only the tailgate using the keyfob,security system deactivates, tailgate can be opened
3 - Shut tailgate (w/out opening any other doors). Locking system should lock tail gate and rearm the security system, if auto central locking is activated.

Mine seems to be failing Step 3, though central locking is activated. And I believe it's been like this for a long time. I didn't find out until this past weekend when I parked outside at my inlaws' in DC, came out to take stuff out of the trunk, closed the trunk and thought the alarm was set, and to my surprise when it was time to go home, the trunk just opened easily as if I never locked the truck!!!

Thanks fellas. I did ask my SA today and he said he thought the tailgate would not auto lock and arm like the sedans do. So, as far as I can tell, we're all fine. But then, my owners manual says that it should lock and arm. Whatever!!!