@Wilburforce: WMT data certainly should be historical, but if that is the case in this instance then the averages displayed today are calculated on positions that I haven't held for at least 12 months. This begs the question why Google is feeding me ancient data and updating it so it has just enough "shuffle" to make it appear dynamic.
Maybe this part of WMT is taking data from serps as they are before any algorithmic penalty is applied to produce the serps that are eventually displayed to users. Maybe it's just not worth G's time to update this site-specific adjustment in WMT Search Queries data, especially as (I assume) most people aren't under the penalty.
All pure speculation I admit, but there has to be a reason for these results reaching my dashboard and the historical data explanation doesn't fit in this case.