Regarding this specific post, the user might have his browser tab open but go eat lunch and then come back, in which case the "time on page" is still not showin

Regarding this specific post, the user might have his browser tab open but go eat lunch and then come back, in which case the "time on page" is still not showing the time the user actually spent on your website. A more accurate metric would be to check for user activity, but then again, the user might be inactive for 1 hour yet somehow actively reading the page content.