In Chrome's F12 tools I see three _utm.gif requests from the article itself. According to http://utmgifparser.appspot.com/, the three requests appear identical except for the "X10 data" ('utme'); not sure of the significance of that w.r.t. GA reporting. Any GA experts care to enlighten?
!0 evaluates to true in javascript so this event is marked as non-interactive, and thus doesn't count as an extra page view and won't be used in bounce-rate calculations.
Presuming the other calls are identical, then their reported bounce rate should be correct.
Looking at the two additional requests, they do currently have the utmni parameter, marking them as non-interactive.
However, the top comment references Google Analytics events on scroll that don't appear to be there now. One of FastCo.Labs folks also made the following comment:
This made me curious as well. It turns out there was a
technical change made at around the same time that is
going to account for some of it. We're running an
experiment now and will update with results.
I don't see the update from him. Given all of this, I would guess that they were triggering events incorrectly and have since fixed it (the article is 3 months old).