Those papers say "language" over and over again, in the titles, in the body of the text. That work confounds languages and their implementations, and make it sound like there is a one-to-one connection between the two (of course, there is not necessarily such a correspondence).

With respect to Ruby vs. JRuby: my student just checked and verified that some but not all of the benchmarks are implemented differently (k-nucleotide, mandelbrot, pidigits, spectral-norm).