Because, as mentioned before, animations for weapon types vary. Korasi is a stabbing weapon, so it can only override weapons with a stabbing attack and animation. Animations cannot conflict.
kebabes
said
:
Keepsake keys don't work on the Dominion Staff.
Dominion items aren't working yet, probably next week.
There are quite some items still left in QA testing, and since they do not have that many time to do them all in one go, they are doing it in small batches.
Throwing weapons also don't work with the keys yet.