Brake Electric Antilock problems of the 2005 Chrysler Pt Cruiser

My 2005 Pt Cruiser is equipped with anti-lock brakes and a traction control system. During a recent snow storm the indicator lights for both of these systmes illuminated. I have just returned from my local Chrysler dealer, who has informed that the lights came on because these systems were not functioning. The reason for this, they believe, is that snow had collected in the wheels. As I understand it, their posistion is that the anti-lock brakes and traction control systems provided on this car will function except during a snow storm with wet, stick, slippery snow. Is this typical of these types of systems? it makes no sense to me that car companies be allowed to provide safetysystems which don't work when they are most likely to be needed. By the way, I live in new hampshire. We get snow regularly. It is frequently wet and sticky.