It's very cool stuff. And I'm not well versed enough to understand exactly how he's handling the grass in shader, but that's fine. As long as I understand that it's happening as an approximation, without "true" physics, that's all I need to know to bring me to my question: why split this simulation into a mix of approximations and the "true physics" of the palm trees (i'm assuming every leaf is boned and driven by the physics engine)?
Why not simulate the palm trees using simple approximated spring physics that often drive interactive cloth simulation? The same way Prince of Persia extended its approximated cloth and rope physics to generate interactive foliage. The same way Crysis did it. The same way I had assumed Uncharted 4 and Lost Legacy handled virtually every piece of interactive foliage except maybe grass.
Seems odd.