No you shouldnt have to. If you look at the edge it should be squared off with an edge above and below. When you sharpen them razor sharp the blade will tend to round and cut crappy. Plus if you remove more material on one side than the other that blade will be out of balance and you will have a shakey lawn mower.
For your consideration, weed wacker string isnt razor sharp but cuts through grass like a champ.
Reminds me, my mower needs new blades
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