That article was retracted because they ran the benchmarks on a debug build which was very different from the release build. On a debug build, coroutines took over 100ms to initialize but on a release build it was maybe 15ms.

They published this article about it. https://medium.com/specto/dont-run-benchmarks-on-a-debuggable-android-app-like-i-did-34d95331cabb