Okay so I think I've pinpointed the issue to be related to my remote starter I had installed before winter.
The starter has a two datalink bypass (one for brake pedal being depressed at start, and one for the key in ignition for start).
What I've just realized is when my drive is complete, and I put the vehicle in P, the green "foot pedal" shows on the dash, but as soon as I press the down the parking brake the pedal light goes away and I hear a "click" from my remote starter box. And then she won't shut off.
As soon as I release the parking brake it clicks again, and voila it will then shut off no problem.
Probably a better question for whoever wired your remote starter. There are a half dozen lockouts to get around for a remote starter, so highly likely some bit of wiring hacking was done to get it to (kind of) work.