A more charitable reading might accept that language names may be used as shorthand for particular language implementations.

In this case:

https://sites.google.com/view/energy-efficiency-languages/se...

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To your knowledge, did such a collection of programs — actually shown to meet that criterion — exist?

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When we emphasize outliers with arithmetic means in "Table 4. Normalized global results for Energy, Time, and Memory".

With medians:

    JS 7.25 times slower than C
    TS 7.8 times slower than C

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Except `--alwaysStrict` and `--use_strict`

So a JavaScript program may have failed as a TypeScript program, and a different program which worked as TypeScript may have been measured.

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The authors provided a repo, including test program source code, that is still available 5 years later.

page 3, footnote 1 "The measuring framework and the complete set of results are publicly available at https://sites.google.com/view/energy-efficiency-languages"