While your tests are indeed objective, I don't think they're very useful. For example, why does your performance test ignore caching?

GitHub's summary page loads 27KiB of data for me unauthenticated, which is about 6% of the 452KiB you're displaying in your first table. The vast majority of developers who browse GitHub will not be loading 452KiB of static assets every single page load.

Anecdotally, GitHub's "pjax" navigation feels about as fast as SourceHut on my aging hardware.