Edit: This PR shows that is likely to be the case. Running in production mode along with some other minor changes shows React running at 88% the speed of Pug. https://github.com/janit/node-templating-benchmark/pull/1
Also, the React component is created on each request instead of just being created once. Unless one's goal is to specifically colour the perception of React, I don't understand that decision alongside the code for Pug which precompiles the template a single time.
(Also declaring the map function outside the component and not creating a closure makes for a tiny extra boost.)
It's disappointing to see that the article took off to this extent given how misleading and inaccurate it is.
Add: on a positive note, this aspect of React is worth benchmarking. Thank you for that.