My theory, from the post: "All of this is likely tied to a relatively new feature called Loud Sound Reduction that only works if AirPods are in an active “Noise Control” mode. So Apple perhaps recently decided that everyone needed this feature enabled, and that’s why they made all these annoying changes to Noise Control? I can only speculate."

And yes, as JamesonNetworks suggested, the cynical side of me thinks Apple execs knew that this would negatively impact a subset of users' batteries and were at least OK with that (despite environmental/shortened-product-lifecycle implications)