Board Thread:Boruto Discussions/@comment-31278419-20170502155353/@comment-734582-20170502160925

Except he clearly knows what the Byakugan is, since he asks for it by name. He also knows it can see plenty of things.

The reason he asks is for the specifics, since he didn't know it could see chakra. In-universe, Boruto simply asks it to check his suspicions. Out-of-universe it's a quick and simple way to tell new viewers about it.

No need to get so upset over such a minor detail.