The manual actually stated that there's a "separate, lower capacity, backup ECU is embedded inside the ECU in a case where the main one is damaged and unable to operate the car. That ECU can keep engine synchronization up to 60KM/h and 3000 RPM".

In one case, my parent's car's ECU (we drive the same make/model) blown one of its coil signalization lines. In that case the car has no backup for example. You need to tow it, because it can't understand that it's output is gone, and can't get into proper limp mode. You need to tow the car.

Cylinder disable on overheat and other modes are proper "limp modes" which keeps car operational when other systems get damaged, but not the ECU.

The automatic transmission has its own limp mode too, which is activated by selecting the 3rd gear and making some other internal pressure adjustments.