Savage, 4.6% is the
All Engines MA (as shown on the chart). I didn't put up the EO MA chart as it was the lateral tracking that was of interest initially, which is the same as the AEMA.
For the sake of completeness, here are the other Airservices Australia (State) charts of interest.
ICN DME is collocated with CS DME (who's bright idea was that
).
There
is a reasonable amount of clear air down there at 11DME...
SID:
As OK4wire has highlighted, the issue is as much about the decision point. It's all well and good having an EO SID down the valley, but what happens if you slot a donk 10deg into the SID turn? You can't go down the valley then, and your performance would have to cope with flying the SID track, at least until you were pointed out over the water.