universetoday - I wondered at first why Systrix was measuring that particular data. Then I realized that it's hard to get actual traffic data for other sites - but ranking positions in bulk is something that a number of analysts would archive and have close at hand.
Positions lost is a lot different than traffic lost. A URL could drop from #6 to #9 and the actual traffic lost could be negligible.
So you're looking at a highly useful metric for your business: traffic. Systrix is looking at data that's important for their business. They're assessing the overall ranking impact of this update.