Well no. It says:

  Yes, with some conditions. You can boot a very minimal version of Linux without the firmware and get it to work with UART and eMMC. Support for USB, DMA, and Ethernet are in the works, which will be sufficient for certain headless systems. Still, many other peripherals require bringup, such as video. Additionally, drivers for power management need to written.

So it isn't clear if this is code in the kernel, or code blobs still to be run in the VPU, and why.

"drivers" could refer to linux kernel, or the drivers as blob downloads, or VPU initialization.

This is separate code (a fork of the Little Kernel project) that runs on the VPU and loads later stages of the boot process, including initialising the ARM core and running the Linux kernel on it.

https://github.com/librerpi/lk-overlay

Edit: The rpi-firmware repo has been replaced by the lk-overlay repo, which is much more flexible.