The advantages of editing online are that you can start working on a file on one computer, and continue on another one. You don't have to install any software...
The audio files can be sent to SoundCloud, but nothing prevents me from adding the possibility to send them to other services, like DropBox, or others. Feel free to suggest what you are interested in.
TwistedWave is not a multitrack editor, indeed. It may become one, one day, but this would be a lot of work...