For example, this post about Minus was published on 9/19/2011. Fuzzy timestamps would cause that to be displayed as “3 days ago” instead of showing the actual date. Come tomorrow, that post will show that it was published “4 days ago”.
You can still see the actual date by mousing over the fuzzy timestamp.
I implemented this with the timeago jQuery plugin. This feature will be available once HTML5Press 2.1 is released, which will probably be sometime before October. If you’d like to take it for a test drive now, you can download HTML5Press 2.1-rc1 from Github.