Monarch man :
you clearly have little idea as to how OMDB is run
Yes my area of knowledge is more European I grant you that, but the UAE surely follows ICAO, no ? although ICAO and RECAT are just giving minimas , each state or airport can increase those depending on the circumstances. maybe OMDB does this or apply something exotic like your description of the reduced wake trial (*). You said at rotation of the elader the follower is receiving T/O clearance ; that would be what , 40-50 seconds separation ? That is impressive.
For Europe the A380 is a CAT A and the 777 is Cat B. The separation minima between 2 CAT A is 3 NM , and between 2 CAT B also 3 NM, mixing categories is the problem not between same types. hence my earlier comment which I maintain.
(*) under the name trial one can do almost anything .and blame someone else if it goes wrong .(Al Wiener if my memory is correct )