It uses FB Messenger for the non-voice API. How is that NOT cloud-based?

That's an interface to it, but all of the voice processing, image processing, logging etc. happens locally and personally sensitive data (like sound recordings etc.) never leaves the house. At least that's how I read it.

Compare with things like Amazon Echo (and I believe Siri and similar services) which send audio clips to a cloud service and do all of the processing there.

Because lag turning your lights on is nonsense?

And yet every commercial home automation suite ties you into the manufacturer's online services.

There is a world of difference between a home automation system that requires an internet connection (processing on their servers) and one that has a "cloud" function (processed locally with remote access).

The latter is extremely easy to find because that's what's been in use for the last 30 years.