It was so dull I had to compare it to the diagram to be sure it wasn't on
backwards...

It hasn't been used much, so I presume I "must" have gotten it into the
dirt, but I don't recall doing that.
Is it possible it came dull?

I realize there is no accurate answer to this, but how many cuts through 12"
fresh pine should it be able to do before it needs to be sharpened, if dirt
is avoided?
1? 10? 100? 1000?