He writes about network of connections, 1st, 2nd, 3rd degree and so on being lost when you change companies, but that is incorrect.

Enough people I know and respect have moved on to other companies that my own network has actually grown. If I chose to apply elsewhere the first thing I'd do is reach out in my own network, not spam recruiters with my Github account.

Your Github reputation can be used in addition to your network, or as a substitute if you have no network, but it will not replace the impact of having others already in the industry/company personally vouch for you.

"Who you know" is still the best way to get your foot in the door, because we are all still social animals.