Apologies for the late reply.

All this plugin does it toggle the xmlrpc_enabled filter that is built-in to WordPress versions 3.5 and higher (setting it to false when the plugin is activated, otherwise WordPress sets it to true by default).

This does not block access to the xmlrpc.php file itself, but disables the xmlrpc functionality.

If the plugin is active and XML-RPC is still servicing requests, then it is possible that another plugin or theme function is re-enabling the xmlrpc_enabled filter.