First, the site defines remix differently than the definition you use. That is logical and very simple.
Second, the fact that you don't appreciate the musical transformations going on is representative of a lack of musical education everywhere. Just because the melody is masked / tweaked / whatever "change" word you want here doesn't mean that the piece is not a rendition of the original. Compare the Bach chorale on
to the original tune -- in the Bach, the melody is certainly there, but it is just one part of a great whole (and you'll note that the melody is not the same rhythm or original key, either).I'm not saying Sephfire is the next JS Bach (though he is pretty awesome -- check out his Extra Credits podcast if you haven't), but his mix that you linked and the chorale both transform an original work to create something more personally relevant to them as artists, and that's exactly the sort of thing the site should be pushing.
Off topic: The site needs more Baroque counterpoint -- any takers?