Others have speculated it was done for liability reasons, that's IMO the most likely explanation. The beauty of civil litigation is there's an easily accessible paper trail. It would be interesting to see whether or not GM has a habit of changing designs without changing part numbers.
However, frequently designs get changed by "marketing" without a part number change, even in situations without possible liability. E.g. wireless routers are sometimes totally revised while retaining the same part number. Apple also likes to implement stealth changes.
Most engineers understand "commonsense", most marketing pukes don't.
Others have speculated it was done for liability reasons, that's IMO the most likely explanation. The beauty of civil litigation is there's an easily accessible paper trail. It would be interesting to see whether or not GM has a habit of changing designs without changing part numbers.
However, frequently designs get changed by "marketing" without a part number change, even in situations without possible liability. E.g. wireless routers are sometimes totally revised while retaining the same part number. Apple also likes to implement stealth changes.
Most engineers understand "commonsense", most marketing pukes don't.