It's definitely nicer to have source than a bunch of opaque binaries. (Is there source for the full boot path? Sounds like they have patches for OpenSBI and u-boot -- didn't see if there was source or docs for the on-die boot rom.)

I just find the "all you need is Linux patches" approach annoying. There are BSD variants and little experimental and homebrew OSes out there that would be fun to run on a capable RISC-V SBC and even if you are using Linux it's still nice to have some documentation to refer to beyond whatever the silicon vendor implemented in various driver patches.