@Saint.V8
Out of interest I did some checks today my 2011 not sure same for older, but probably.
Test 1.
Unlock whole car.
Open upper tail gate and click lock shut.
Lower hatch still works.
Car will not lock on remote.
Test 2.
Unlock tail gate only from fob, so doors stay locked.
Open upper tailgate and click lock shut.
Lower tailgate button still works.
Close upper tail gate (still latched) as low as possible.
Reach in and operate lower tail gate.
Can also operate upper tail gate.
So the car has not sensed the upper tail gate being closed/locked as I can use the button a second time when normally, open on tail gate and close locks all again.
So to answer the original question that stick idea is not really suitable as the car/tailgate cannot be locked.
J
So would somebody be so kind and pass on to Goldie that the idea is a no as far a security or dogs accidentally operating lower tail gate.