I just now snipped the yellow wire with the black stripe, and it worked as advertised up thread!
My only guidance is that I did NOT go via the glove box, but instead accessed the wire harness from the footwell, by removing a small, black, snap-in kick-panel that blocks the space between the glove box hinge and the firewall. Once I contorted my body down there into the footwell, I immediately saw a "loose" bundle of wires that had been attached to a factory-tight loom via a couple of small, black zip ties. Within that loose bundle was the aforementioned yellow with black wire. I never saw/noticed the "grey switch", but it's possible it's there and I'm just an idiot. I snipped the yellow with black wire, and capped each end with a tiny plastic acorn nut.
Long story short, I'm happy as a clam that the remote car starter now works as expected, and will allow us to get the kids and groceries loaded up without killing the engine. Feel free to PM me if you want any other input or tips.