EK keeps cross fleet training to a minimum
I guess that is because there is no big difference in the main elements for any pilot: life style, roster pattern or income between A330/340 fleet and the 777 fleet.
Don't forget also that EK roster bedding system allows most pilots to select few destinations of their liking every month.
All EK planes are wide body, so as a pilot you worth the same value in the international job market.
Let's take EY and GF as an example from the region, they stopped NTR capts to join directly the wide body, you have to join on the 320 fleet. I personally don't mind if I stay on the 330 fleet while QA hires pilots on the 777, but why the 320 pilots have to suffer for long years before they transfer? (if they will ever transfer).