Not EK - but with a group I was just dealing with, a couple of flights had longish delays

I received an automated text message regarding the delay and what time it would now be leaving together with details of what time checkin would clsoe ( which was now based on new departure time )

If the airline has informed passenger of rescheduling, then cannot see why it would expect people to turn up based on the original time

In a case where no communication is made to confirm a delay, then I would aassume normal checkin time requirements