https://patents.google.com/patent/US20040144166
Airflow is measured by the MAF sensor. The MAF value goes through the TB model and manifold model to get an in cylinder aircharge value. The throttle model(DD torque table values) is used to get a second air flow value(see Bill's Torque control ETC system post). This also goes through the manifold model. Both are compared at the in cylinder aircharge value which is represented as air load or absolute load. Just as the MAF sensor is critical to the airflow measurement, a critical part of the throttle model is the TPS. If the sensor fails then the MAF value is compared to this table and limited to the in cylinder values. Stock values are between ~30%-50% load if the TPS sensor fails for safety. With a digital MAF you are not limited as much as analog MAF sensors were, so a failed MAF to load table is less important.