Last modified: 2011-03-13 18:06:45 UTC
When not restoring all Versions on Special:Undelete usually just some problematic are not to be restored but the vast majority is. The default behaviour when undeleting a page is to restore all Versions anyway. Therefore it would make sense to have all Versions' chechboxes be checked by default so the user has only to deselect just the few bad versions instead of having to click hundreds of good ones.
As it stands, if no revisions are selected, then the software restores all revisions; the SQL to do this is simpler and less taxing than if the software restored all revisions using specified individual timestamps. An improved deletion mechanism is planned; please search this bug tracker before posting further.
Please note that that's not the proper way to remove items from a page's history -- they will get restored the next time someone tries this trick, defeating your efforts. If items *must* be removed due to privacy or legal reasons, this is what the Oversight/Hide Revision extension is for.
(In reply to comment #1) It wasn't meant as a change to the SQL-handling but as an enhancement for user friendlyness and something to happen just on the HTML/JS/ PHP-Level for the user interaction. At the moment it is most likely that if someone does not want to restore all Versions that he most likely wants to have nearly all chechboxes selected.