Jason Snell, referencing Craig Federighi’s comments on the most recent episode of The Talk Show:

You may not remember this, but before the Apple Watch came out, there were many rumors that it wasn’t able to get through a day without a charge. It’s clear that Apple made battery life a top priority, perhaps even the top priority: This thing better last all day. And so everyone was incredibly conservative with power and memory.

The result: They overshot. Most of the people I know now report that they end their day with their Apple Watches reporting 40 or 50 percent of remaining battery life. Federighi admitted that there was a lot of extra memory and battery life available to them when building watchOS 3, because they overshot so much. And that’s why watchOS seems almost impossibly better than watchOS 2, given that it’s running on the same hardware.

I had a hunch that this was the case and I’m more than happy to have it confirmed.