Y'know, DC really went to great lengths over the years to disguise the fact that Clark is so much shorter than his leading lady...standing on boxes in close-ups, forced perspective for long shots, all of the tricks of the trade. But every now and then, they'd slip up and you could see just what a wee little man he truly is.
No wonder she's in shock, I mean the amputated part of her arm and leg!
Dr. Novakaine
Supes must have missed that health class. That, or he had that misconception from the start and no one wanted to correct them because they knew he could punch them through time.