Driving on one tire that is a lot shorter (or taller) can reek havoc on a drivetrain. Not necessarily sure that is the case here, though.
About a 1.6" difference in diameter. For revs per mile, the larger 285/65/20 tire, there is going to be about a 4.5% difference in rotational speed.
I just don't know what the threshold is for the stability control system.