RTF is a global modification that replaces all towns in the game.

This is well thought out, as skeletons don't have flesh or muscles, so they wear clothes that don't fit.
And in general, originally, there were some improved archers who were replaced by crossbowmen. So, skeleton archers are essentially the undead version of the improved archers.
Here's the info: https://mightandmagic.fandom.com/ru/wiki/Блог_участника:Рон54/интересности#Скелеты_лучников