It now does a transaction per undeleted Flow revision. It would be better to do it per overall undeletion operation. However, the page ID is passed to ArticleRevisionUndeleted, and it can vary by archived revision.
Checked in betalabs - no new deletion issues have been found.
Clicking 'Delete' on Flow board page redirects to action=delete page that states that there are certain number of revision for this page, e.g. "You are about to delete Talk:ET1 along with all of its history." where "history" is a link to the page history. However, Flow page history does not clearly list those revisions (and, of course, there is no way to select a specific revision from the history page).
Wikitext pages have more transparent workflow for deletion - their history page is titled as e.g. "Revision history of Mavetuna5813" and allows selection of a certain version for deletion.