Jeff, I've spun the airspeed completely around climbing over weather with a frozen up pitot in a Cessna back at the dawn of time. Aircraft climb may factor in to extend the duration or degree of overspeed indication.
The relative frequency of overspeed/underspeed indications during pitot freeze up is not the issue. The issue is that it can go either way and what happens when the airspeed indications increase significantly above actual. From last years posting, it would appear to be downright ugly. I really don't think this issue has been put to bed.