I always read that as "I'm not detecting a keyboard. If I'm wrong about that let me know by hitting F1. (And if I'm right I don't want to waste time by booting, because you'll have to power down to fix this anyways.)" Because that was in the time before keyboards were hotpluggable.

Some early computers with a key toggled the keyboard power, rather than preventing someone from turning off the power switch... I guess it was more important to keep people from typing things than it was keeping the system powered up. The 80s and early 90s were weird times. /shrug

Sound logic. Personally, I have never come across that error when a keyboard was connected.