“All” is all content on the fediverse, across all instances with which your home instance is federated. It will be similar for all instances, because most are federated with the big instances and those tend to have more posts and interaction.

If you only want to see the feed of communities on your local instance, you can just browse your “Local” feed.

I think it’s from “The Founder” about the guy who turned McDonald’s into a national chain.

Thick as a Brick