What you’re saying is my understanding too. All those things are 80s tech that back then operated in separate isolated closed loop servo feedback when working right and pissed everyone off when something went wrong because they couldn’t just go out and fuck around with the carburetor until it worked right.

Part of what made obd2 so great for so long was that it gave you the actual measurement to pair with a symptom that would tell you what to test to figure out what part was messed up.