And I don't really understand why they don't follow their advise. Saving a single byte on Google front page can potentially save terabytes of bandwidth. I know the idea of "developers are expensive, hardware is cheap" but when you serve trillions of search queries, hardware is worth considering. The 8 MB you get don't come from nowhere, there is a server somewhere sending them to you.
And improving user experience for billions of users is not a negligible advantage either.
Maybe it is a sign that Google is ready to be taken over by a less bloated company. It is, after all, how Google came to power, by being efficient and to the point. Just look at to original Google home page compared to its competitors.
This actually gets back to the issue of web bundles. Google doesn't have to worry about the 8 MB because they have an extensive CDN, but smaller sites have to save every bit because they are being charged for it.
If Google can leverage its CDN to serve the smaller sites, everyone wins.
I mean, kudos to Google for (probably) not cheating here, but that's a low score.