You haven't missed anything... The very first AWD 911 was the 964 Series carrera 4 (the 964 being the variant before the 993). In that generation the 911 Turbo was still RWD, it was only with the introduction of the 993 series that the Carrera 4S model (with more power and, I think, a wider rear body) was created, along with the first of the AWD 911 Turbos
The only other AWD Porker is the rare 959