It is pretty clear now that the whole point of CI400 was to encourage delayed flights to make up some time en-route.
The sensible NOTAM would have read "....when operationally necessary use of up to CI400 is encouraged/permissible"
instead they decided to go with "Every flight will no be planned at CI400" No explanation, nothing.
Of course very high CI's are normal day to day ops at many other major carriers. To make up delays, protect connections, curfew arrivals etc. EK just chose to implement this in the least transparent and logical manner.