Those are beautiful houses. I love the idea of doing something like this, but: A) I'm lazy, and B) I live in a place that has a ton of humidity. I wonder how such buildings would fare in a non-arid climate?
Looking up Earthships can be a good starting point (though many of those are desert climate focused as well, it's not a necessity) for further research.
That's why our typical "vernacular architecture" is log cabins, not mud brick structures. Different advantages and disadvantages. Different construction process. Different materials. But still more sustainable than concrete.