We don't worry about it - the monster's stat-line tells you what they do and don't have (if anything), what the specific models is armed with is totally irrelevant, even more so that the models in a warband.
If your models for skeletons include 2-h weapons, so what, just say (for example) the magic to reanimate them wasn't strong enough to give them the strength to wield them to it's full capability.