The iPhone does not spy on its owners and users. The Apple Watch is an accessory of the iPhone. Ergo, it does not spy on its owner. QED.
And looking at their documentation isn't proof.
A sniff of the network while the device is on can sometimes point out 'unexpected' communications with unknown devices. If it's a different platform.
I'll wait for the guys that love doing that to see if spying is going on.
/johnny