man, I wasted so much time looking for more information, and I didn't even need it. I already had all the information I needed *sigh*.
alright, here's the manga you were talking about, although the databooks are real. here sasuke is saying that itachi became chunin at 10.
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and here is itachi becoming chunin
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and in the same scene, sasuke is announcing his entrance ceremony into the academy.
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and that's all the proof you need, lol. I know everyone is like

. but let me explain.
we KNOW that sasuke was 13 when part 1 ended, kisame or sasori said in part 1 that it's been 7 years since oro LEFT, that puts sasuke at 6 on the pic with itachi be 10 or 10.5. if you say that sasuke was 8 or something, that means that oro was already gone, and that was when itachi JUST entered anbu.
so that's it. no matter how you look at it. since we KNOW that itachi entered anbu at 10/10.5, if you say that it was 2-3 years later, you will also increase sasuke's age by 2-3 years, and once again making it impossible for itachi to have seen oro at all, since he left when sasuke was 6. and this is MANGA.
it really sucks that I did all that extra searching for nothing U_U