Here's the thing: the weapons table is more or less a relic, and pretends small differences in dice size and damage type actually matter. Those oddities are a sort of by-product of that. They could have boiled it down to a couple lines of text for simplicity's sake in the Basic Set, and retained the same amount of diversity and choice. But the halberd and glaive being identical, as the OP pointed out, gives me the impression nobody has really thought about it for too long.