Speaking as an educator, multi-sensory learning, which Super Why offers, helps in developing critical thinking and problem-solving skills at an early age. It's not just 'watching a show', it's an interactive learning experience. Books are essential, yes, but educational shows like this serve as a supplemental tool.
As a teacher myself, I can't condone this, but I've got to admit it's pretty smart. Just don't make a habit of it. Subs have it hard enough as it is!