Studio Neat's Dan Provost, writing at Medium:
When the original iPad Pro 12.9" was introduced in September 2015, Phil Schiller demonstrated the reasoning for that sizing by illustrating that the width of the new iPad is the exact same dimension as the height of the 9.7" iPad.
This has the advantage of essentially having two full height iPad apps, side by side.
Now, imagine Apple doing the exact same thing, but with the iPad mini.
As I tweeted earlier today, an iPad like this would be the best of both worlds.