php support

After a recent migration to Plesk 12 all but one of my sites are running PHP 5.3.3 as Apache Module (as they have run on previous Plesk versions). One of them is failing because it is set to fastCGI - on which it was not designed to work. The strange thing is that when I go to hosting settings...

Configure a domain with PHP-FPM support (in my case via Nginx). The pool config is created as expected. Then in Plesk turn off PHP support for the domain. The pool config remains present (with timestamp of the switching off, i.e. it was recreated, although it should not have been).