These are both great points. When I wrote the post, it didn't occur to me that I could inspect the emitted bytecode. In hindsight, including that would have made the explanation much stronger.
To be honest, this is my first time really digging into performance on a JIT runtime. I learned to code as an astronomy researcher and the training I received from my mentors was "write Python when possible, and C or Fortran when it needs to be fast." Therefore I spent a lot of time writing C, and I didn't appreciate how aggressively something like HotSpot can optimize.
(I don't mean that as a dig against Python; it's simply the mental model I absorbed.)
The realization that I can have really good performance in a high-level language like Clojure is revolutionary for me.
I'm learning a ton from the comments here. Thanks to everyone sharing their knowledge -- it's genuinely appreciated.