Board Thread:Theories and Speculation/@comment-995176-20170316230844/@comment-1018594-20170317000617

Cheating and not getting caught was a component of the written portion of the Chunin Exams, and that was way back in Part I. The format of the Exams has changed each time we've seen it.

Also, Boruto wasn't banned. He was disqualified for using Kote, which the Hokage (Naruto) specifically had banned from the Exams.