Oddly enough, there is what I assume (hope?) is a typo in there, on p38 it says "Your watch can only get a notification. Use the phone paired to your watch to answer the call." Then later it talks about making and answering calls. I would have assumed, like the Samsung Gear series, that you could swipe to answer a call using the watch as a bluetooth speaker/mic paired with the phone (even without NumberSync). Huge dealbreaker if it doesn't actually work that way.
Pretty sure that feature is not available yet. Verizon says it will be available after an update to messages+. Not sure about att. The capability is there. Carriers just need to find a creative way to integrate the same number as your phone. Verizon has opted to used messages+. Please correct me if I'm wrong.