Explaining such a high ground speed is easy, A321. Last night, with 40 kids on board, our Vapp was 153kts. Add a few more adults, and still air it's easy to get to 155kts.
I think flap 3 makes more sense for an A320 than a 321. Although the landing geometry is better for a 321. I just think the savings are marginal at best. You would only have flap full out for about 30 seconds to a minute longer than flap 3 anyway. So your going to save a minimal amount of fuel. Add in using MED auto brake or any reverse thrust and those marginal saving are deminished further. Miss the exit that gives you the quickest route to stand and your now starting to cost money.
On the face of it Flap 3 fuel flows will be lower than flap full fuel flows. I think this is what Airbus have confirmed. Add in all the other "real world" factors and flap 3 landings become a marginal cost saving exercise at best, and costly at worst. Throw in just one over run or tail scrape, and all the saving you ever made from flap 3 landings have just evaporated.
If companies were serious about wanting to save fuel then they should be applying pressure to ATM service providers to sort out the airspace, particularly in Europe. There are massive savings to made here, in the region of 500 to 1000kgs per sector. That's how you save fuel, not trying to eek out 10kgs by eroding saftey margins, that don't work in the real world anyway.