I still have to disagree. We saw points yesterday where the Kiwis were ahead yesterday up wind, and they didn't just extend and disappear over the horizon.They have clearly changed the boat to be faster upwind (or LR have downwind). Last days the bigger difference has been upwind and that has allowed TR to bounce back when LR hit them and pass when they get a slightest chance.
It's not several knots, but probably 200 m on a beat, which turns to 1 km when TR wins the start.
Look how fast TR came back, when LR forced them to a bad leeward rounding and got a 200 m lead. And look how fast they spread the distance when they managed to pass.
Also the start was even and TR manage to get 20 m lead before the boundary. That was almost enough to roll LR at their leebow.
I think these boats are really closely matched. Even more - I think like you said, the Italians upwind tactics and speed have perhaps forced the Kiwis to give up some of the downwind speed to match them.