Apple

I think when Apple announces battery life for watches, the measurement is for the current watch on the current software. Over time, yes your battery holds less charge, but also, the software gets new features that the newer hardware handles just fine, but the older hardware starts to struggle with. Apple doesn't provide data for newer software on older devices. There's no spec sheet from Apple saying, "if you upgrade your series 5/6 to WatchOS 9, you should expect this new, lower battery life."

But we all know newer, better features are going to use more compute - that's just how technology works. So you either 1) cut off older devices from the newer features, which users get grumpy about, 2) provide the new features but don't say anything about the impact or 3) provide new features but say how it impacts older devices and maybe provide toggles and system controls to enable/disable. I don't think #3 is really in Apple's DNA - that's more of a Microsoft approach.