A/F/R gauge for tuning

Can you explain this. If the charge is unburned then more oxygen is present in the exhaust. The sensor reads the presence of oxygen not unburned hydrocarbons. An HC meter could do that if you had a 4 gas analyzer hooked up.
When I see lean misfire on the dyno my o2 sensors show lean.
This should be also true with a rich misfire, yes? Still unburnt O² that the sensor will pick up? This would also say too lean but honestly over rich.