When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
my guess is 450h starts out in electrical mode and awd system is controlled/linked by the gas motor, so the button is useless since it is only good for speed up to 15mph...
the rear wheels are only driven by the electric motor. my guess is that they dont want to discharge the battery and/or do not want to overheat the motor.