To be clear, you'll be using this system automatically if you install Keybase on your phone or desktop. It'll just work, and you'll have a private key on that device. As you add devices, you'll collect keys. If you remove a device, that public key will no longer be a part of your identity.
If you want to use PGP on one of those devices, you can. And you can strongly connect it to your other keys, as the graphs in the post show.
This should be easier. From a "regular" non-PGP user perspective, you needn't think of this as managing keys, or adopting a more advanced key system. Instead you would just be managing your devices and installing Keybase.
That's our hope anyway. (Disclosure: I'm one of the people working on the project - https://keybase.io/chris - thanks for the kind words about the project)