The tumbling variant isn't an opposed roll but rather a reflex save. The tumbler still needs to make the appropriate roll to tumble w/o AoO but with the variant all opponents would get a ref save to ignore the tumble and still make an AoO. The DC for the Ref save is the result of the tumble roll. So if you have +14 to your tumble check you can still get attacked when you tumble past an opponent. It won't happen often but it can happen