That's fair criticism. Whilst the setup shown in the article is synthetic, the experience is from working on real world projects. I've worked on a bunch of projects which had about 3000-6000 barrel files easily, and these then lead to every file in the project always being included. The total amount of files being loaded was somewhat around 30-60k, depending on the project.

I did the exact same thing as described in the article and wrote a custom test runner for jest that bundled the test files with esbuild before executing them. Even though bundling introduces a costly overhead on its own, it was still about 60% faster to bundle + run the bundled code vs not doing it. Bundling can also be amortized because it only needs to be done once per test run vs once per file. That's where the real gains came from, because in jest every single test file constructs the whole module graph from scratch.

I haven't checked myself, but there is likely improvements to be made in node (or other runtimes) to address this. Hopefully, some folks get inspired by this article to look at that.