To be fair, Mandreel has done a lot of work with Google, and you can see practically all their games are on the Chrome Web Store and made for it. So unsurprisingly Google has optimized for them. There is nothing wrong about that, of course, just pointing out that they are not "a third party with no ties to anyone".

Second, while Emscripten is a Mozilla project, you can see that it works with Chrome as well: Links to bugs filed by an Emscripten dev (me) appear in that blogpost, in fact - those bugs are filed to help Chrome be faster, and nice progress has been accomplished, one of those bugs was just closed in fact (it's cool stuff, read it for more info - Chrome was much slower than Firefox on that benchmark, and now it's faster on it).

Finally, the point of the blogpost is that all benchmarks need to be treated skeptically - there is no such thing as a perfectly unbiased benchmark. So we need to just be aware of that, and not consider any specific benchmark to be "the" benchmark of the modern web. That's all.