They offload some of the compositing and some of the fetching and asset flattening server side, and then serve up to the device with custom protocol the pre-rendered flattened data anything that can be done server side. That is exactly the same way those other accelerator products already work for mobile.
While it's a nice design, it's been done. The limitations and issues are well know as well, like having trouble with private intranet sites and VPNs or that because all the requests come from a few centralized IPs, geoip doesn't offer any benefit (GEOIP is a hack anyways but sites use it and users get confused when their pages think they are where ever some colo is). It also creates a single point of failure which, pedantically, is counter to the design of the internet.
I was a little inflamed by the video's first statement that browsers have been built pretty much the same as they were since the beginning without many innovations. Sounds like marketing spin. I can name several notable amazing advancements in browser design since the days of WordWideWeb at CERN and Mosaic. A good number of amazing achievements around security for sure.
Also, on top of that, you know what happens when Silk touches Fire? It's not pretty.