Before item 6.2 of Setup manual tried to run updateStats.php and got error about class 'FlaggedRevs' not found.
Then I did items 7 (Enable FlaggedRevs) and 8 (Update MediaWiki's database schemas) and returned to item 6.2. UpdateStats.php worked succesful!
May be move item 6 (Enable collection of article review statistics) after item 8?