Board Thread:Episode Discussions/@comment-1181222-20180726120028/@comment-5001176-20180801040050

Amanim wrote: Even though I'm done watching this anime for good. Will Boruto please stop calling Naruto an old man since for once he doesn't even ask Naruto how old he is.

I don't think "old man" in this context is meant as a reference to Naruto's age in the literal sense, but more in the sense of a (somewhat disrespectful, I admit) slang.

IIRC Naruto himself used to do the same thing when he was a kid in some cases.