My conspiracy theory is there is something inherently rotten at Apple and it is simply not possible to build a smartwatch that never mind can match the feature set of the apple watch but also the levels of battery efficiency on the iPhone paired with a smartwatch different than the Apple Watch. I don't know this for a fact but I am sure multiple cheap ish Chinese watch vendors would not choose to intentionally drain the iPhone battery if they could avoid it.
Pretty much spot on https://ericmigi.com/blog/apple-restricts-pebble-from-being-...
I think there’s a simpler explanation. Apple’s always uses a type of product metric that most companies don’t use. Those competitor products don’t care about phone battery drain, so they aren’t even trying to do anything about it.
I mean, it's Apple's whole strategy to create an ecosystem of devices that all work really well with each other. Having had some insight about how chinese manufacturing operates on the low end it's much simpler than that, they just don't really care about things like not draining battery life. Their products are built to a price point and they are aware of that. If it could be built to the same price point without heavily draining battery life then it would be.
It's not just a theory. It's well documented that Apple has a bunch of APIs and protocols (like AirPods proprietary low latency wireless instead of Bluetooth, NFC was not allowed until years after Apple Pay) that are not available to 3rd party developers. They will sometimes open things up after they've given their own products years of head start because apparently owning most of the ecosystem and having undying brand loyalty from their users isn't enough.
Actually for many years even to build regular Bluetooth devices that did anything besides audio, you needed to add a special chip (Made for iPhone chip) to your hardware to verify that it was an authorized Apple Accessory. Pebble had one, but any 3rd party apps that wanted to send data to the watch (like Uber app, sports apps, random indie apps) had to get allow listed to communicate with accessory devices like Pebble.