Were the reversion edits also excluded in the "Net non-reverted edits"? For each reverted edit there is a reversion edit that reverted that edit to the previous version of the page, so when a wiki has less reverted edits it has also less reversion edits. If the reversion edits were not excluded that explain in part the decline of non-reverted edits, that is in part because there are less edits to revert the vandalism.
