@IMACOP it doesn't need to cut bone to makes blade become dull, even cutting flesh can makes blade duller...
example is kitchen knife, just to cut vegetables and meat, the knife become dull and need sharpening....
moreover bandits's swords that never got maintain properly, by the time MC using it, the swords basically just a dull blade used to crush or stab enemies rather than slice them... yet MC using that dull blade to cut the head cleanly, and not only one head, he using same sword for few clean head cutting until the swords can cut no longer...