I read that, but her statement left me confused. In particular, did she intend to say that the S1 ended the day at 65% and the S2 ended the day at 25%? That is what she wrote, but that does not seem like a benefit. Or, was her intent to say that both watches end at 65% when in Airplane mode and both watches end at 25% in regular mode? And, does her clause "at the end of the day" imply that she had a full day of use without a recharge prior to the 4 hour workout, or did she recharge? This one is confusing, because the numbers to not match. A 4 hour workout with GPS active should have burned 80% of battery, which exceeds her EoD number.
My hunch is that she is trying to say that by putting the AWS2 in Airplane mode, it disables GPS, which saves you about 10%-15% hour of battery burn. So, battery burn for a 4 hour AWS2 workout with GPS drops from 75% battery burn to only 35% battery burn without GPS. This reconciles with her other consumption data and Apple's web site commentary on battery consumption during workouts.