It's amazing how people read what they want into stuff!
Then for the 'banging drums' it's a case of "click... whirrr... replay conspiracy theory/ anti-google vitriol...."
As I see it, this is what it means:-
1) "We have recomputed data that might have impacted some sites" -- in other words, they have iterated over the Panda data (you know, the data they said was updated periodically, not constantly) at least once since launch.
If you've made changes to your site, at least the part that Google has managed to index (maybe not all 10,000 pages you binned!) at the instance(s) they rerun the calcs is in the Panda data.
2) "There’s one change that might affect sites and pull things back" -- is saying that they have only back-tracked with one change.
Yes, sadly for you, Matt is not talking about your site (why would he be) he's talking about his algo and a change that softened it a little.
3) "It could help as we recompute data." -- a fuller response might have been: "look, we weren't anticipating such wholesale decimation of websites inflicted by spooked webmasters. Now we're way behind the current reality in terms of indexing all this and recalculating the link graph, etc. Frankly the index is now a mess of 404s, 410s, 301s, canonicals, noindexes and nofollows and it's going to take a while for the our picture of the web to catch-up with the new reality."