Enums are one of only a few places where there is significant deviation, I don't believe that makes it 400% less efficient.

Maybe read the paper and see if you can figure out their reasoning/motivation :) https://dl.acm.org/doi/10.1145/3136014.3136031

One thing to consider, is that with JavaScript you put it in a .js file, point a HTML page at it, and that's it.

TypeScript uses a ton more than that, which would impact the amount of energy usage too, not to mention everything running the package registries and what not. Not sure if this is why the difference is bigger, as I haven't read the paper myself :)

But if you do, please do share what you find out about their methodology.