Do you have a reference for that statement? Can you post the link? I'd be very curious to see what that algorithm looks like.
No I don't. It was somewhat of a guess from resourcing information on OBD system and scanner reference materials. I do know that these other parameters are measured by the ECM for whatever reason, along with amount of fuel used and the number of combustion cycles. Therefore, the ECM would then be able to estimate what the engine temperature "should be", and comparing that to the reading from the ECT sensor to determine if the engine is indeed running cold and trigger the P0128 code for "engine running cold" if necessary. If the readings are out-of-norm, then my guess is that there should be another code for "engine temperature unknown".
This is how I would design the algorithm:
If the ECM reference is Cold, and ECT reading is Cold, then no fault exist.
If the ECM reference is Cold, and ECT reading is Hot, then a possible fault exist. Trigger a code and put the cooling system in "safe" mode.
If the ECM reference is Hot, and ECT reading is Cold, then a possible fault exist. Trigger a code and put the cooling system in "safe" mode.
If the ECM reference is Hot, and ECT reading is Hot, then no fault exist.
The problem here is that under the first scenario when all indicators showed a cold engine, once the ECM triggered a P0128 code it will operate the cooling system at the maximum "safe" mode regardless.