The company I work for supplies interior components for pretty much every OEM in the world, up to and including complete interiors. Having personally been responsible for several GM interior programs (HHR, Solstice/Sky, Corvette, Cobalt, SRX, and a few more) I can tell you the issue is called out-gassing, and it comes from all the plastic parts in the interior, not just the IP top pad. Advances in plastics have reduced this significantly in later model cars, but it is still an issue. Having said that, it can definitely be made worse by the use of after market chemicals applied to the vehicle interior, such as Armor All, Scotch Guard, etc.
The condition you experiencing is normal.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)