Figure skates and hockey skates have a curved blade. The pressure exerted by them would be much higher, due to the much smaller surface area in contact with the ice. I'm surprised these scientists either don't know this or failed to mention/consider it.
Yes, ice is slippery even in contact with shoes. But compare the two. You will travel much further gliding on ice skates than you will in your wingtips. There seems to be something to the pressure and/or friction angle after all.
Not only that, but as I'm sure you know, the surface of the blade that contacts the ice is not flat side to side (ie the cross section), but concave, so that the part actually touching the ice is very thin.