Motion sensors don’t provide localization. Gps on cellphones are only really accurate to a few dozen meters.
You can couple gps and motion (and changes in gps location) to fudge it. Which is why when you diverge off the route navigation provides… it takes it a moment to figure it out. In the display, they “know” you’re on the road so it doesn’t have to be that accurate, they just guess what lane you’re in based on direction and such.
They’re certainly not going to know what seat you’re in.