In a AF intra EU plane the economy is split in two by a small curtain, in one part you get a minimal amount of food in the other just a drink. That is the product difference, not a lot to be able to complain about.

An Alitalia EU plane has not the "curtain" and in their system such class does not exist. So I understand I can not pretend an upgrade to biz. S is mapped as Y or B.

On the second leg, still operated by a partner (Cityjet) for AF, the plane is so small (Avro) there're just 2 class (biz-eco). It seems the fare gurus did not really noticed on such routes they do not really offer the Premium economy.

The funny thing is that the same flights sold with AZ numbers are more expensive and less flexible, just "economy". I.e. less FB miles.