I conclude from my 5 odd years flying EK and reading threads here that:

EK has no systematic opup policies. Period. The rev management model is poor (EK. Can afford it for now with their fabulous growth) so Y is oversold frequently. This makes for full Y cabins so they do loads of op ups but without any consistent prioritization algorithm. This gives rise to a lot of speculation but bottom line is they have no consistent systems on this count.

If you want rational opups,n fly an airline that does opups based on rationale, like CVV scores etc.