"We simply learned to sail the catamaran up on the foils even upwind," Spithill said in reference to the San Francisco comeback.
America's Cup: Inside Team New Zealand's speed machine
"Both us and the Kiwis had tried this technique before the match to no avail. On 1-8 we realised that we were slower than them and that without upwind foiling we would have lost.
"Ironically, in the last edition of the Cup in Bermuda Team New Zealand had a mysterious device that helped the crew control foiling."
Spithill may be referring to a device Team NZ's skipper and wing trimmer Glenn Ashby used during racing. It was a hand-held device he called his "little x-box console" that controlled the shape of the wing.
Other wings on the Team New Zealand boat were controlled by traditional winches, however Ashby was able to make micro adjustments to the wingsail simply by adjusting toggles on his control panel.
Spithill will lead Luna Rossa at the 2021 America's Cup as he seeks a third title.
Speaking to RedBull.com last year, Spithill admitted he was looking forward to the opportunity to have another crack at the Kiwis after being too conservative in Bermuda.
"I'm not going to lie to you, I want payback and revenge. That's a big part of it," Spithill said. "I love competition and they're the best out there right now. For me, this is another opportunity to go against the best."
"I hate letting down my teammates and you carry that burden as I was the skipper and I take full responsibility. The two main things I learned from the last Cup was 1) we were too conservative and 2) I didn't go with my instincts enough on and off the water."