Not a new thing. Bags can make connections tighter then MCT will allow. Been that way for years. And unless you're flying internationally, where bags have to fly on the same flight as you, there is no requirement like this for domestic flights.

I had it happen to me the first week DCA re-opened after 9/11 - flew YVR-ORD-DCA and the bag was at the bag office for me, making the earlier connection than I could book because of MCT. I've seen it several times since.