Parts of the seat are not leather - the extending section on the TI for instance or the scuff panels on the edges of the seats and the pockets on the backs of the seats, but the majority of the wearing part of the seat is leather; the seat back and squabs.
I'd say a small part is not leather, certainly the parts you have mentioned. The one thing that turned me away from Saab was the diminishing amount of leather in the seats. My wifes 02 plate Saab has even leather door panels, a real nice quality car, with lots of leather.
Since I'm here, I looked at both the Ti and the Lusso. The Lusso I bought is red with tan interior, this and grey are the only two colours that Alfa supply that have the whole of the door card and the trim under the dash in the overall trim colour. Natural and red leather for instance have black door trim cards with a coloured insert.
So how did this influence my choice? As I said I wanted the tan interior, because I wanted a light colour on the inside of the car, the Ti that I saw, and others since have a black roof lining, and that I do not like, to dark. I also prefer the more supple suspension on the Lusso, folding mirrors and cruise control (is cruise on the Ti?) I do know there were several things that made the Lusso tick the boxes for me.
I do believe that the word lusso is Italian for luxury, that it is.