Flying for an airline across the pond from EK with similar weather conditions, I know that the temp issue is mainly for the 320 family. We also did it on the 330/340 after they removed it from the SOPs. However recently they generalised this habit for all airbus fleets. Now it is back on the 330/340 and also written in the A380 SOPs (as an option). That can be te reason why you saw it on the 777 as well.
I have never had the ECAM message on the 330 or 380.