Not quite understanding your logic. The second line is correct. The third sentence is wrong. The Alfa settings are for Toe-Out and this is normal on front wheel drive cars because the engine torque will cause the wheels to want to Toe-In. The standard Alfa settings causes inner wear because the Toe-Out is too much. Modifying back towards zero eliminates inner shoulder wear (not as you state).
If you want to go into more detail the real problem (or asset) is the 'fast rack'. Only slight steering inputs move the inner wheel dramatically so that it acts like an anchor as you go into the corner. The outer wheel is taking the weight of the car and doing most of the steering. The inner wheel is helping by dragging the car round.
So standard settings give a false sense of agility. The modified settings save the tyres.
With negative scrub radius, universal on FWD cars for thirty years or so, power-on creates toe-out.
The object of toe-out is to increase the cornering effect from the inside wheel, without using too much ackermann compensation, which tends to corrupt steering 'feel'.
The fast rack is a red herring as the inside wheel 'drag' is, as explained above, a function of the ackermann angle. Since the inside tyre is more lightly loaded it needs compensation for the outside tyre generating maximum cornering force at a slip angle which can be as much as 5 degrees.
Most wear occurs during normal driving when the steering angles are small, hence the need for the front wheels to be parallel. It does seem that the 159, particularly in Ti form is very sensitive to the toe setting (possibly excessive bump steer?), and so when various people advise 0.00 (parallel), they really mean that. Despite what a garage may tell you, it really is not that difficult to get it spot-on. On my traditional Dunlop optical gauges it is quite easy to see the effect of adjustments of as little as 1 or 2 minutes.