You memoized some of the computation.
"Think rate is fixed" glosses over activities with compounding returns. Learning!
Better abstractions and heuristics can have an enormous impact on problem solving efficiency.
First-principles thinking is a powerful hammer, but it's expensive. Over-use it and you'll get nothing done. Under-use it, and you'll do nothing original. Knowing where to use it is the trick, and that's _also_ a skill that can be improved over time.
My brain has compressed/chunked patterns so that I can immediately see what the optimal move or set of candidate moves are instead of having to determine them more computationally.
I'm not sure how that fits into the framework of this article. Something like the number of calculations remains static but total work done per calculation increases.
Much of the debate in this comment thread is a result of these concepts being fuzzily defined in the article itself.