It seems that for cache items that have 'function' defined but no 'purge-function', ezcache.php --purge will never purge anything. The 'function' will be called instead. The patch fixes this.
Related, earlier fix:
Tested on DFS cluster and normal FS:
php bin/php/ezcache.php -s ezflow_site_admin --clear-id=template-block --purge
does exactly the same as
php bin/php/ezcache.php -s ezflow_site_admin --clear-id=template-block
Both will call eZCache::clearTemplateBlockCache(), this is defined as a 'function', not a 'purge-function'. It just sets expiry, and does not purge anything. (BUG)