My theory would be that when the new engine rule was approved some thought or knew that Minardi's budget was not on the same level as the rest of the teams and therefore Minardi was given a dispensation to use a restricted 3 litre V10 so Minardi wouldn't have to develop a new chassis adapted for V8 engine and would also not have to buy new 2.4 litre V8 engines for 2006 season. But as we all know Dieter Mateschitz bought Minardi and there was nothing he could do as all agreements were in place for the Minardi team. That is why STR will use V10's while the rest of the teams will use V8's.
On tororosso officiel site (a site that i dont like), i see nothing about it, no update, no new news. Maybe its not the final release or it is, maybe website will be update later.