Can you explain how this is not "calculated engineering by engineers"? My impression from the video is that these are architects and engineers building these.

It's very similar to the work of Shigeru Ban who has done a lot of work with paper tubes and timber. Some of his work is visually spectacular. There are some photos on his wikipedia profile.

https://en.wikipedia.org/wiki/Shigeru_Ban

It’s Indonesia, engineer doesn’t really mean what we think in the west. It’s more that someone is passionate about something, not that they have a civil engineering degree and are building to some code. There are engineers like we’d think in Indonesia of course, but they’re unlikely to work on a western lady’s pet project and are going to be a lot more expensive.

So more like a software "engineer" ?

Sort of, but if the software engineer had never had access to CS material and worked in a company where practices were based in CS so they naturally picked it up. These are villagers that build small homes without machinery and very basic tools, and haven’t learned from experts.

The particular style of the house in the video is just one many possible designs. I’m sure there’s nothing to stop one from using bamboo in a more calculated design.