We definitely need to inform players about the improved quick cast feature, and not just inform them, but convince them that the old quick cast, which they're used to, is a bug, and the new one is the real deal. If I forget to inform them and they rage quit, it will be my fault. If I inform them, but can't convince them, we'll have to play without the new quick cast and without some other useful features.
As they say, feel the difference.
And what is all this for? To fix a bug that rarely occurs in the actual game, has little impact on gameplay, and is something that many don't even consider a bug.