I saw someone on reddit say it was a mistranslation. No idea how accurate this is.

Is it possible that they are saying "more than 10 years"? It has to be a mistranslation or an error on the anime part. In episode 24 Naruto said it's been 15 years, so it's odd that they made this mistake twice now.

Or maybe they just don't give a rat's ass about the timeline and they just say whatever they think sounds good. But it's probably just a mistranslation. It was pinned a long time ago that Boruto's time happens at least 15 years since the war.

Maybe they just wanted to give a good estimation of the time.

Like, I mean, why should they bother saying it's been 16 years rather than just 10 years. Like if you ask around with people about certain things they did in the past, they'll probably go with a year, though the correct estimation would be months, people usually refer about ten months to an year, because it's easier and safer to say and has probably doesn't want to look like a weirdo, calling out accurately the number of days, hours and minutes(even seconds) it's been, I'm pretty sure, sitcoms and all use it as a joke to indicate someone's weirdness.

Though there could be an alternative reason to all this. Maybe the war actually ended at about ten years ago. Like I mean, the fourth war, as we all know, ended with Sasuke and Naruto's battle(or them against Kaguya) But as the anime started to show these events and things the manga didn't show, like the Kaguya ruins and mysterious Zetsu survivors. Maybe the remaining Zetsu's were still needed to be disposed off, like they did talk about meeting other zetsus and ruins like these.

Or maybe they included Toneri's attack against Earth as part of the war. Considering the war had some part in it. Like the statue being missed, causing civil war until Toneri came to Earth.