Maybe they are they next to a window or under a sky light.
> or if they could use location data to figure out that 'this Apple Watch is in the middle of a large field, so he must be outside'.
Could be in a tent or other temporary structure.
Don't talk like that, its a self defeating mindset. You are likely as competent as most Apple engineers (the 10x benefit from less inhibitions and tons of energy.
The people working at apple are like most of us here, curious and driven. Apple has a lot of money to throw at people who bring in experience whereas you and I are individuals who do not work in the field of "figuring out where things are using computers." So we obviously are not experts in the field and not familiar with existing and emerging solutions for the problem.