[ggm]

At some level this feels like a consequence of a design decision heading to the instruction decode logic. You can map from the Octal groups to the ALU wires and traces and gates in the 8080. They don't have to line up any more, we've moved. beyond that, but if you had the original chip naked and ran it, or ran a simulation, a "mechanistic" relationship between the octal groups might emerge visually?

It also feels like how the 'hidden' instructions get found.