Mattax hit on this and it should probably be expanded a bit.

“….If you do resurface on a machine, then the shoes ought to be arced to match…..”

When new brake shoes are installed, especially on drums that are worn or previously turned, the arc of the shoes is smaller than the arc of the drum. This results in a just a small contact patch between the drum and shoe until the material wears into the arc of the drum. Back when 4 wheel drum brakes were the norm it was not uncommon to hear complaints about poor stopping after a brake job until the car was driven for a few hundred miles.