It was in the release notes as:

MDL-34481  Ensure that completion is recalculated on next cron run following changes to completion settings

However we do normally post to let you know when things are fixed but this one got missed.

By the way, be aware that a cron run is still required after changing the completion settings before everything is up to date. This is done for performance reasons since changing the completion settings could result in lots of completions which could take a long time to process.

Simon