6:9 is selected only because of today standard and lower costs compared to 4:3. This project currently needs to follow whats most common on market to reduce costs and bring first product as soon as possible.
4:3 is same as non "island" style keyboard, I agree 4:3 is cool but I doubt it will ever come back, same as "island" style keyboard will be replaced again with old style key edge by edge..
We can all suggest what we want to see in computer from this project, we can propose butterfly-keyboard but it will only postpone first product release. We should concentrate on what is useful and achievable. from currently standard components on market with being aware of cost of that same things.