Went into the Apple Store and asked about this - the manager said that it was due to bandwidth limitations, but it could be added in a future update if they can get the hardware to handle it. Very disappointing, especially as my contract includes inclusive data but not inclusive minutes.
Bandwidth limitations? FaceTime Audio is very low bandwidth. The Watch can stream video from the camera app and high quality music which are much higher bandwidth.
I think "bandwidth limitations" might be an easy form of temporary "technical limitations".
If there's bandwidth to stream regular calls, then there's no reason why FT Audio calls can't be streamed. I think it's not so much a technical limitation as 'out of time' for the development team in this v1.0 of iOS for the Watch. Stay tuned I'd say.
Also, there's no reason why Apple Watch Siri should not be able to calculate a percentage either. I was surprised when I asked her a simple % question - "What's 20% of 400," she referred me to using my phone.
Yet, she can tell me so many other mathematical answers.
So...strange...
You can say "<Number> times point <Percentage>"
So "400 times point 20" gives you the attached answer.View attachment 552322