Depending on how engrained they are in a mix, it looks like it. A vocal with multiple panned harmonies and loads of delays and/or reverb might be more difficult to extract though.
I'm sure you could use to to re-master stuff to a degree or maybe use it for extracting samples from songs.
As to the sound quality... You could see some comb filtering and phasing artefacts potentially. I wouldn't trust the cake videos on sound quality. It's going to take un-biased testing to check that one out.
To me, it looks like a cool tool for a bit of fun, but I wouldn't ever imagine using it when making my own music.
But for maybe analysing in further detail the construction of pro songs, it could be good. As well as taking samples for people who do that sort of music.
But I don't imagine it to be much special. The high and low stuff is just going to be a simple band pass filter. The stereo component is going to be probably a M/S type process with something like Channel Tools and phase cancellation blah blah. I'm sure the maths isn't too complex. With the right routing you can probably just do it with channel tools and an eq. I may of course be wrong here, I'm only speculating.