I'd agree with the KA Pilots frustration. Normally if you are the lower Aircraft you would naturally get to be number one over an Aircraft above you at ELATO. That's what's happened to me many times when I've been the lower or the higher Aircraft.
So what if the Boeing is 20 to 25kts faster....it would still take way too long to get far enough ahead ( usually need at least 10 nm trail )
They should have asked Asiana to slowdown and KA to speed up a bit.
Letting the Aircraft above go first only creates extra separation issues for ATC involving off track headings for the lower slower Aircraft to obtain separation, speed difference isn't enough.
So basically the lower guy gets screwed around way more than necessary.