EK haven't changed the contract or manipulated the 5 year rolling average figure.
The problems is that most pilots haven't bothered to consider how the ERP actually works.
The rolling average is catching up on the pound. Soon it will on the other currencies. ERP will decline to nothing and in the course of the next year there will be a 7.5% salary cut for those who have been doing well on the ERP.
EK will continue to take revenue in highly valued currencies and pay you in Dirhams so they will continue to benefit from lower wage costs.
Why do you think the UAE hasnt depegged or revalued. Every day the dirham drops, all the expats building the country get paid less. They worry about inflation but that's a problem that the workers must pay for too. Why would they dream of upsetting this little arrangement?
The ERP is an advertising gimmic - nothing more. It only partially addresses short term currency fluctuations. It will not address the long term and deliberate devaluation of the dollar.