Things like Norway with Frozen and the Bakery, and France’s Bakery are usually the only World Showcase offerings to open with the park (although I swear I’ve seen Mexico boat ride open early too, but not sure that’s normal). So adding Ratatouille to that schedule doesn’t change anything.
Last time I was at EPCOT they allowed you to walk from Mexico to Norway -or- from Canada to France. But, everything from Morocco to China was not opening till 11 and they turned you around if you started heading that way.