This is not something I reasoned out in my bedroom. It is knowledge passed on from someone to me who learned it from someone else and then reinforced during my own experience. The next time you see some outdoor furniture, picnic table, adirondack chair, etc take a peak at the feet. Then give it a wiggle and for bonus points pick it up and move/rotate it five or six inches. The obvious answer is that the smaller leg means that you you do not need to find as large of a flat area for the leg to stand on. It means that the leg can rest inside of a little divot on your lawn. In addition to reducing wobble it makes it less likely that someone stubs their toe and trips on the corner, but I am less sold on that one.

More importantly, it is just wood, go try it yourself. If you don't have the saw blade on a SAK/leatherman and a piece of scrap wood try scissors and a spaghetti box or a couple of pieces cardboard taped together. "Learning" something from a comment by that ornery dude on HN is not the same thing as seeing it in practice.