“Five minute read” has become a joke, because the number is often a guess pasted on an essay that wanders. Used honestly, it is one of the kindest things a publication can do. It lets someone decide, before the second paragraph, whether they have the time you are asking for.
We count words and divide by a calm pace, then round up. A short note should say it is a short note. A lead should not pretend to be a caption. If a piece grows during editing, the number grows with it. If we cut, the number comes down. The point is not precision to the second. The point is not lying.
There is a second courtesy underneath the number: structure. A dek that delivers the argument. A pull quote that is actually in the piece. No surprise PDF at the end. When the minutes are up, the reader should feel they arrived, not that they were kept.
We will get some of these wrong. The correction is to change the piece, not to hide the clock.