I just rewatched the start of GBR/NZL. I don't think that GBR entered early (although the umpires did call that as an offsetting penalty for NZL). Looked like they were a length or two away from the box at 2:00, at least on the TV timer.
PM, Ainsle most certainly didn't turn back to help. He slowed, looked to be sure his chase boat was responding, and kept going. He actually told his crew that they were still racing until the RC or umps would call and award the point. That didn't happen, so he radioed in, and when told he had the win, they sailed to the dock. I am glad that he showed some concern for the NZL crew during the post-race onboard interview, especially after his horrible lack of such comment during the presser after nearly killing or disabling several guys on JPN in the opening series.