411A:
"Now, if the crew truly believed that another engine was either failed or not producing adequate thrust, then the two engine procedure should absolutely be used, which requires a reduced plap selection for approach/landing".
Have you watched and listened to the animation? You don't seem to have grasped what they actually did. I agree that it is difficult to believe that something so basic went wrong.
They (correctly) shut down No. 2 engine.
They flew the pattern using the throttles (correctly) for Nos. 1, 3 and 4 engines and set up for a three-engine approach and landing.
When they got to slowing down all throttles came back to flight idle. When power was required again the GOOD No. 3 engine was left at flight idle and whoever was applying the power pushed forward the Nos. 1, 2 and 4 throttles.
The No. 2 throttle was, of course, connected to a shut-down engine and putting that throttle forward was as much use as putting t*ts on a bull.
It is obvious to me having listened to the CVR that it never at any point occured to any of them that they were now conducting a self-inflicted 2-engined approach so therefore never considered the 2-engine out procedure.
If they had used the perfectly good No. 3 engine they would have been in the bar by now and would have probably picked up at least five medals each!