yeah, the rule is 2 players over 20. my thoughts are that because players around 19-23 are forced to move to lesser teams with lesser training and lesser technical abilities i think it would be a good way to keep players at big clubs with the good players and introduce them into the team slowly but surely rather than having a chance and if you don't take it you're practically out of the club. i think for a club like inter, the likes of rene krhin and joel obi would get regular playing time with mancini, quaresma, vieira, matrix, cordoba etc without the pressure of first team football and it would be beneficial to the afore mentioned senior players too. if krhin and obi go on loan to somewhere like chievo, they may not get regular minutes there either whilst training with lesser players and coaches anyways.
also, it seems, italy is the only major country that doesn't have a "reserve" league as england, france, spain, germany, holland and even brazil do.