Not really... you now know how to install Gentoo, a rather eccentric Linux distribution. To know how Linux works "from the ground up", you'd need to make a star

Not really... you now know how to install Gentoo, a rather eccentric Linux distribution. To know how Linux works "from the ground up", you'd need to make a start of understanding the kernel source from top to bottom. Then you can go in to learning about the userland things, such as the init system (which is different in Gentoo from most other Linux distros). Doing a stage 1 install of Gentoo or some similarly masochistic distro-installation trick (Linux From Scratch, hurrah!) means you're good at reading an install guide. After you install Gentoo, could you immediately go and write a kernel driver, or even set up NFS, since you know Linux from the ground up?