It may seem a "stupid stunt" to you on the basis of your personal experience, but it's a very safe, stable and essential part of a bushplane's flight envelope on the basis of mine.
Incidentally, small ripples and wavelets are no problem, but squally conditions are best avoided. Small tires would steepen part of the lift/drag curve appreciably, perhaps uncontrollably. Glassy lakes demand a degree of care, especially after lifting off the water.
I'd be interested to read the official report on the accident to which you refer.