Agreed, a great question
Alex, if you are going to ask the question, could you please challenge the usual suspects with a definitive answer s’il vous plait ?
As a passenger I’d expect the MCT to be terminal time, i.e. from disembarkation to gate close time. But disembarkation can lead to issues, arriving from EDI @ CDG, you end up nowhere near the main complex and if you’re unlucky enough to be connecting to another remote stand flight, the usual behaviour of ground staff crew is to shut up shop early, to give time for the “last bus” to travel to the aircraft and passengers board, as if the bus was an extension of the terminal. Which means that in reality you have to minus the bussing time from the actual gate close time.