I think the concern is for people who want to use a MC system for 2ch music. So, like you said, for MC you could just use the LFE channel for a sub, but if you want to also use it for 2ch then you'd need some sort of crossover, either in the player, the pre/pro, or an active on the mains (set mains to large, surrounds to small, sub off).
I'm not sure how I'd want to set mine up yet, so the versatility is nice. It seems like the Dragon has some bass mgmt provisions but earlmarc must have found it lacking when he investigated?????