I don't think he channels ONLY the historical figures themselves - he summons them along with all their general accoutrements, otherwise they'd all be naked, wouldn't they? It'd be like the Terminator, only instead of getting kill-happy cyborgs, you'd get confused and embarrassed naked historical figures, which wouldn't be much use in combat. And really, you can't have the Shining Knight without a flying horse. 'Twould not be proper.