Intuitively, I see the bevel placed on the inside of the strike radius to force material in the desired directon, like a spade. I realise that a wood chisel is used in the opposite orientation when cutting a slot (when the chisel is used with only a small angle to the grain of the wood), but finishing of the edges is done in the same manner as a hoe.
The question is -- why is there conflicting advice on the choice of edge orientation, and whether any actual difference informs this choice.
An ILO publication on Rural road maintenance training mofules for field engineers has an image showing the bevel orientation. An earlier edition (offline only) indicates that this prevents bounce during use.