I think Apple has very rudimentary tracking to help save battery life. Even if Apple had a toggle to allow for much better tracking, people would still get irate and complain about battery life because of the app. It is really a no real win for Apple, in my opinion.
I don't think that's the case. All the sleep tracking apps use the data that the Apple Watch collects anyway. You would think the native one would be even better, but it isn't. Apple has a ton a resources, they bought Beddit and their sleep tracking is by far the worst out of all the sleep trackers.
I raised a ticket with Apple years ago, such as when the Apple Watch is off the wrist, turn off WIFI/Bluetooth, sensors, etc, so save battery. Then when you pick it up, it kicks in to gear! Pebble did this and it saved power. Apple Watch, no.
I also asked about turning WIFI/Bluetooth off when it detects you are sleeping and turn it on when you wake up. Nothing.
There are ways to save power and I don't have any skill compared to the Apple Devs.
Currently, I am using a Garmin Vivomove Style for sleep tracking (I also use it for Ant+ to send HR to my cycle computer).
Another basic thing. We are on Watch OS 8 and there is still no way to send the HR to something.
Honestly, I love the vibration of the Apple Watch (it's brilliant), the convenience of Apple Pay (again, brilliant), the simplicity of the straps (an absolutely incredible design for watch straps), but as a fitness device, considering how powerful it is, it sucks! (for me and my needs).