Sure, yes, but the comparison in question isn't the only comparison, it's just one of many. Letting people see the difference visually for themselves is more tangible and less questionable that putting up two file size numbers and claiming they're equal quality. And if you think about it, it similarly wouldn't completely be fair to BPG to turn up the quality so that the JPEG looked reasonably good, because the BPG file would be in the range of diminishing returns per byte.

It is fair to point out that JPEG falls apart below a certain compression threshold while BPG doesn't, even if it's a little bit apples to oranges. I prefer the way @enriquito said it https://news.ycombinator.com/item?id=20419900 but I disagree with the hyperbolic claims in this thread that this comparison is outrageous or complete spin or cheating. It's a data point that has some actual merit, and BTW happens to agree with the other data points we have.