I can confirm this. A video will be uploaded showing this bug soon, although in the video the squids are underwater. The footsteps can still be heard, though.
Just tested this. Still happens in 13w09b.
Ok. Sorry about that. This could be considered confirmation that it happens outside of superflat though.
Wesley, I realized that one second after I posted it, and Cube, I checked three times all with different keywords. Don't just assume that people didn't check at all.
The video file itself is too big to upload, but here's a Youtube link. Copy and paste if you have to.
https://www.youtube.com/watch?v=oLDXezbhj-s