Why not use flashrom?

[kuba2k2]

Flashrom is a popular tool used mainly for flashing PC BIOS chips. It supports a wide variety of SPI flash chips, it's optimized for speed and error-free transmission, and it's safe and well tested.

Your tool is good for booting the BK in SPI flashing mode, but I just don't see the point in writing a new flasher when a good tool is already available, and probably simply installable in most Linux distributions.

I'd consider either updating the guide to teach flashrom, or making the python script execute flashrom internally.