Well, one, because the headline isn't from the researchers, its from a popular press report (not even the one posted here, originally, this is secondary reporting of another popular press piece) and isn't what the paper claims so it would be odd for the paper's authors to conduct benchmarks to justify it. (And, no, even the "up to 95%" isn't from the paper, the cost savings are cited per operation depending on operation and the precision the operation is conducted at, are as high as 97.3%, are based on research already done establishing the energy cost of math operations on modern compute hardware, but no end-to-end cost savings claim is made.)
And, two, because the actual energy cost savings claimed aren't even the experimental question -- the energy cost differences between various operations on modern hardware have been established in other research, the experimental issue here was whether the mathematical technique that enables using the lower energy cost operations performs competitively on output quality with existing implementations when substituted in for LLM inference.