This is a fun piece... but what killed off the horses wasn't steady incremental progress in steam engine efficiency, it was the invention of the internal combustion engine.
According to Wikipedia, the IC engine was invented around 1800 and only started to get somewhere in the late 1800s. Sounds like the story doesn’t change.
Sure, but if you look at more complex picture of engine development you could just as easily support the proposition that programmers are currently not in any danger (by pointing out that the qualitative differences between IC and steam engines were decisive when it comes to replacing horses, and the correct analogy is that much like a steam engine could never replace a horse, a transformer model can never replace a human).
Not detracting from the article, I think it's a fun way to shake your brain into the entirely appropriate space of "rapid change is possible"!
