[tzs]

Which of these biological differences in capacities and functions make it so that girls should not be punished by physical pain but it is OK to punish boys with a physical pain using a method that often leaves permanent scars and lasting psychological damage?

[CGMthrowaway]

Men bear greater physical risk (war, dangerous labor etc) and boys/young men have always been subject to violent "rites of passage" that prepare them for this.

Girls and women receive greater physical protection, as required to manage reproductive capacity and long‑term demographic stability.