The current raucous, howling laughter of the Cackle ability suits it better than the conniving, sneering laughter that Witching Hour has right now, so I'd rather not see that changed. More importantly, I think this sound effect change implies that someone on the dev team is paying some attention to Witching Hour and the witch theme in general.
AlphaPsa said the "witch theme was officially on (his) pipeline", or something along those lines. This was in response to the old thread we had running about the future of the witch theme. Now, the recent patch that went alive with the revamp was started by SoE, re-taken by DOG and implemented, so yeah, I suppose AlphaPsa coded the cackling into witching hour. Still, however, we had the whole issue with sound for a long time, so probably DOG themselves place it. Still, a neat detail.