I believe GP is predicting it will backfire on the users who buy into the ecosystem, not Github itself.

Because Microsoft effectively building a monopoly on OSS. I'm happy now, because the product is amazing but it's always sain to have everything controlled by one company.

I understood the point to be that to do all these things well is very difficult for a single product / company. I worked at a startup where our solution was to replace five other solutions. Only customers with the simplest use cases found that it worked. The complexity from the breadth makes achieving the requisite depth for a good experience difficult.