Yeah, as I understand it there were some fairly nasty BIOS compatibility issues with keyboards that try and do full spec-compliant NKRO, and some older OSes mig

Yeah, as I understand it there were some fairly nasty BIOS compatibility issues with keyboards that try and do full spec-compliant NKRO, and some older OSes might have had issues too. The specification says that software which requires the special boot protocol need to request it, but in practice it often doesn't, so most keyboards only support that format and are limited to 6-key rollover plus modifiers. A few hobbyist keyboard designers have tried doing this the proper way and quickly regretted it once they sold enough keyboards to be exposed to real-world systems and their behaviour.