There would be little benefit to using the Dex-Cool if it was not the "factory fill".
And merely flushing and getting "every drop out" doesn't matter either. The actual main benefit to using the Dex-Cool is found through the initial break-in period which is when the Dex-Cool coats the aluminum engine parts with an extra protective coating. It can only happen on a new engine and anytime thereafter, even the tiniest amount of "regular" green coolant contaminates the cooling system for good. Therefore you might as well just stick to a good quality standard coolant.