[stonogo]

No, it is entirely correct. Auto makers in Asia and Europe had engine-control computers such as some of the Bosch Jetronic family, and each manufacturer had a bespoke diagnostic interface -- many of which persisted long after OBD-II arrived. These automakers were relatively quick to tie their existing diagnostics tools into the OBD-II port (often speaking a different protocol along the same mechanical connection).

US auto makers were still running throttle-body fuel injection (no ECU required) or were licensing German ECUs (and not tying them into the OBD-II system). Almost all the US automakers were desigining OBD-II compliance with minimal integration into the rest of the engine as a misguided cost-saving measure. So for about a decade in the US if you plugged in an OBD-II reader, it would let you know if there was an emissions-control problem (bad O2 sensor, bad MAF sensor, etc) but be completely silent about other (often critical) engine problems. This situation was obviously stupid, but it took automakers a long time to change course.

Today, most so-called OBD-II dongles are actually microcontrollers which speak multiple marque-specific protocols, auto-negotiate which one to use on startup, and give you scads of information. But at its heart, OBD-II is an emissions-focused standard, which is why it's mandated by EPA regulation in the US and is one of the "measures to be taken against air pollution" specified by the EEC/EU.