Polar bears are white because their fur is clear, and acts as a prism to pass light down to their skin, which is actually Black, to absorb it. The filaments of fur are not hollow - do not contain air. There is air trapped in the pile, but the air does not cause the white-ness. The only 'pressure' that acts on polar bears being white is evolutionary pressure, which is a very long bow...
As for the Harvard grads not working it out, the statistic is obviously invented. 67% of you already realise that, and 29% suspected it. The rest are a bit slow.
This 'riddle' is akin to the familiar instructions lists you give you children, with "read all the instructions before beginning" as the first instruction, and "only do number 4 number and 9" right down near the bottom of the list. It's a trick which relies on you seeing complexity where there is none, on trying to complete a difficult puzzle when you are only asked to comment on it.
The question is quite clearly stated: can you solve this riddle. Asked to a kindergarten class, I'm sure you would get a few odd answers, but most would simply say NO. An adult is more likely to try hard to think around the riddle and find something that fits almost all of the propositions, and submit that, thinking it must also somehow apply to the last one (which is doesn't).
The answer is "NO".
The lesson is don't overcomplicate things.