Title says it all.

See for example api.php?action=query&list=categorymembers&cmtitle=Category%3AValuable%20pages (replace the category with something that exists). There are calls to $this->logFeatureUsage( 'list=categorymembers&cmstartsortkey' ); and $this->logFeatureUsage( 'list=categorymembers&cmendsortkey' ); which don't seem relevant here, as those parameters were not passed in.

If the calls are meant to be there, the API help needs to be fixed to explain what's going on here.