No, I don't think it will work harden, but I'll tyell what I do think. I think that when these blades get a final sharpening and buffing, a worker may get a little gung ho and not keep the blade as cool as it should be. The heat right down on the thin edge can get a little of the temper messed up in a small way. That same knife, sharpened a few times may get ground that tiny little bit back into the good steel that didn't get hot right down on the edge. As the old factory edge gets ground away, you have moved back past where a little over heating may have happened.
Just this old farts opinion though.
I knew a lot of the old guys when I was a kid, that when they got a new knife, they right off sharpened it to get rid go the factory edge, no matter how sharp it had been out of the box.