No, the tree demonstration would map exactly as is onto a modern game engine. One viewport shows you your scene, the other shows you the design behind the scene, which you can tweak with realtime feedback. Playing with these controls leads to discovery.
An engine inevitably limits you to whatever it was designed for. Compare this to tree concept, which starts as bunch of lines, then experimentally moves into day/night scenery of a tree in wind.
Exactly! This is what we do, and that's the trend that game development has been following for 10 years. If many tasks are dependent on a coder it indicates your engine is more of a programmer's SDK rather than a modern game developer's toolbox.
As long as designer (whoever) needs to call onto a developer to do a tweak or do some technical bit, there's a huge impediment to creativity. Pipe dream goal of such experiments is to present tools that vanish out of sight.
We build the kind of stuff shown in these experiments every day - this is what game engines have become, so the examples in the video should not be surprising or "impossible/impractical" at all!