It sounds like you may have pre-maturaly unbuckled your car seat. I did not have time to read this entire thread but next time check to see if you still have your seatbelt on or not.

Here is NORMAL for me
I pull into garage after forward, reverse.
Engine will sometimes turn off from the Eco system during the process but will turn right back on again to complete the parking maneuver
Once you place the car in PARK the engine will again turn off from eco THEN
unbuckling my car seat tells the car "I am getting out" so, naturally, the car turns itself off.
Good feature as you don't really have ANY reason to need to touch the START/STOP button when exiting the car.

 

Hmmm, Tim, I've had that happen perhaps 6 times in my ownership, always and only when reversing into my garage and engaging Park. I know some Jaguar features "learn" the driver wants, so I've only guessed that my car has learned that I'm nearly ready to shut it off. Ndabunka, I'll try your technique today, put it in park and disconnect the seat belt. Sounds like a fine technique!

 

Shut down technique did not work for me, just to follow through.