Beta Cluster wikis are storing IP data for longer than 90 days in the recentchanges table too. Since rECHU is not installed there, purgeOldData cannot be run due to the hard requirement of $this->requireExtension ( 'CheckUser' );.

In order to comply with the Wikimedia privacy policy, a script should be created and run to clean all that old IP data, setting all rc_ip data older than 90 days to an empty string.