I believe it's more of a shift to Tesla no longer continuing to support classic cars. It literally has nothing to do with autopilot hardware and doesn't need autopilot enabled, so it's clearly an artificial cutoff; at some point Tesla will simply tell us to buy a newer car or deal with it, I guess. At least they aren't intentionally slowing us down like Apple! Imagine installing 9.0 and suddenly having a 12 second 0-60 or something...