You are wrong, it is how it works in sage Naruto, once you get a rare, you cannot get the same rare again until you get the 2 other rares.
No, it's you that wrong. In every treasure you don't get dupes only if you reach every single time the hidden counter and you never pull off a lucky early drop. So, in sage treasure, you get no dupes only if you actually used exactly 60, 120, 180 scrolls. If you were lucky and you got, lets say Ao before the 60th draw, lets say it was your 58th, so you don't even know if was or not the 60th if you just used draw by ten option, then the streak of rares resets like if you never drew in that treasure and at your 118th pull you can get again Ao.
This works also in jinchuriki treasure, but is slightly different because there is also the interaction with yugito nii that have a different kind of counter (40, like in edo tensei), so is hard to foresee the true behavior.