I’m not sure there’s a problem here, knee-high boots over leather pants strikes me as a combination that’s going to cause you some trouble with encumbrance.
The ‘over’ layer on feet is reserved for things like snowshoes or galoshes you wear over regular shoes, doubling up on encumbrance there is much worse than an occasional incompatibility between particular clothes.
If anything, it seems reasonable to swap the knee-high boots on the reenactor for regular boots with no leg coverage.