Well, I don’t think that article is trying to cover the end cases at all (how often you critically succeed or fail). That’s a different argument than I think they even bother trying to touch on. I think all they are trying to cover is that if you set the right difficulty/target number for something then the statistical chance of achieving that outcome (the binary one of strictly success or failure, not one of where on the middle or the edges the numbers fall) would be the same. Well, ok, good to know as a game designer that you need to be aware of designing proper targets for outcomes, so that says to me you are then free to look at the type of rolls you want to use for other uses. If you ALSO want to be able to affect things outside of success/failure then using a pool like Codex does instead of a straight d20 definitely affects that, and uses that to the advantage of the system. Or more accurately, it allows the player the option to make that decision (since they can always choose to roll with just 1 d20 or multiples, after all).