@felixthecat really sorry if it sounds like a show, didn't mean to.
110% correct saying there different 777 ... correct!
So ... for the pourpose of the exercise lets use the most penalty situation ... old 300ULR with RR at MTOGW for an OAT +40C ... my question is ... how is it possible that in 4.3 miles a twin engine jet aircraft isn't capable of reach 400 ft AGL?
It is possible only if the takeoff is performed above the MTOGW for that day (rwy condition and elevation, OAT).
To be certified as a twin eng you need to meet a minimum required climb gradient. The airplane has to perform this minimum required climb gradient between 35ft and 400ft...
... but it would be interesting to see the EO SID for DXB 30R ...