Bruce Barnett wrote:

It sounds logical, but as I picture it, the one corner wears faster,
and to hold it rigid you have to do so without the edge near the
center. This seem unstable like a 4-legged chair with one leg shorter
than the others.

Yes, exactly. As long as someone or something (the tool/blade holder)
firmly holds the chair in its original orientation with the 3 longer
legs in contact with the ground, the one shorter leg cannot contact the
ground until the 3 longer legs are all equally shortened or ground down.