I've had my V 7+ weeks and think I have tried just about every thing with the remote door locking. I have a theory about your problem. I think you tried to verbalize it in your post, #1 in this thread. Your question (at the very end) seems to have been ignored by everyone. I want to answer it, IMHO.
Yes, your symptoms point to a latch problem, not a light problem.
All by it self, we might conclude that there is something wrong with the light. If you took it to the dealer, they probably put it on their test box and confirmed that the computer was not told that the hatch was open, even though it unlocked when you stuck your hand in the hole and lifted. Normally, the hatch latch stays open and closes the Hatch-open circuit so the computer can light the cargo light AND (this is key) keep the other doors from re-locking in the normal time-out (30 seconds seems right). It is the fact that you have two problems that can be associated as I have done that makes me think, you have a latch or wire problem tied to that hatch latch. (I'd guess those two are about equally likely.)
You said you were waiting for a part. Does the part go into the hatch cover (like a latch part?) or does it go over on the right side, a plastic light fixture into which the cargo lamp
fits? It is possible but a little unlikely that without that bulb to light, the hatch would not signal that it is open. I don't really want to go there without schematics. I find the shop manual void of complete wiring specification. If anything goes wrong, I will have a hard time figuring it out.
Anyway, Put your money on the need to fix the signal from the hatch latch to the microcomputer that controls both the cargo light and the re-lock of the other doors. I have unlocked all doors (I changed it to one press about a week ago. I like that) and opened the hatch any number of times. Sometimes working on things in the cargo and eventually closing the hatch and opening the driver's door and driving away. Have never seen the behavior you describe.
I guess you know about the hatch-only release on the remote? That unlocks the hatch for single use. press the button with the trunk icon and the tail lights will flash twice. For a time, the hatch is unlocked for your convenience. However, when you close it, you cannot open it again unless you re-apply the hatch release or you open all doors with the middle button on the remote. Again, mine works just like that and just as described in the manual.
Any problem with the hatch-only release on the remote?
Let me know if you can find behavior not consistent with the scenarios I presented. I've been a professional trouble shooter for many years but I am glad to sharpen my skills by being wrong and being told about it. Thanks in advance.