Recent experience....

Flying SYD-DXB with a J Flex ticket. I had both auto-upgrade selected AND notifications set on EF for any Z availability.
Spoke with EK call centre a week out, and they confirmed no award seats available, however only 3 of 14 seats had been booked (which corroborated with EF).
T-96 - I checked the EK App, and sure enough an upgrade was available. No auto-upgrade / no notifications from EF.

On the upside, it coincided with the Skywards 25 Million Members promotion, so I managed to pay 25% less in points.