As far as I know, nobody's bothered with copyright for uploading videos. And they shouldn't have to, either, nobody's going to try and rip the song from the video when they could get a sound effect free version elsewhere.
Well, for many reasons I, and many others too, upload videos without Sound Effects. But even if you have the effects in, the Audio is still property of someone else, and I've seen Accounts deleted and Videos removed because People didn't have permission to.
Basically you're right, and Audiosurf Videos are in Accord of "Fair Use", yet not entirely, which is why the entire Video is also Property of the Artist of the Song as they gave the Audio for it. Many record companies don't care, but some do and forbid the upload.
But most people don't know sh*t about Copyright, neither when a video is legal, nor how to make it legal.