Why does the Legion in Oblivion look Medieval?

I'm wondering if there is a lore explanation for why the Imperial Legion (at least in Cyrodil) looks like they are wearing medieval platemail when in every other depiction I can think of from the other games they are wearing what looks to be like imperial-era Roman soldiers outfits. If there was a lore explanation for this it would be extremely satisfying for me. Or was it just a stylistic choice taken by the developers of Oblivion? Very odd if it's the latter because it is completely inconsistent from all other depictions.