Methinks you aren't giving them enough credit.
The catch that struck me was the server that gets told "this post is #12345" when it only holds up to #12340. What does it display for 12341..12344? But then again, this may be so rare I simply haven't observed it. After all, I've rarely seeing any offset greater than "post N+1 of N".
Some days, things make sense to me, and some days, they don't. It happens that your explanation was simple enough (or I was aware enough) for me to understand the concept.
I think there has been a lag of as much as four posts the last two days. Even refreshing hasn't helped.