I would be curious to see results with Firefox as well. I like to see people testing assumptions. I agree with the author’s primary point- it’s likely highly dependent on what tasks you are doing with the browser. The results are still interesting nonetheless.
For my use case, it's quite obvious what's draining the battery: addons. Every trick and feature meant to preserve privacy and to remove visual trash will significantly impact load times, responsiveness, and battery life. It's all worth it to me, but there's no doubt a web without tracking and ads would easily double my battery life.
Never, ever venture out on the web without a content blocker.