It's the compression!
The color resolution is a factor, but not such a big one. In this case the compression is the biggest factor. If you assume that both the 4K Edition and the 4K Cineform contain the same material, 4K Cineform contains more than 13x the information (as stated on the timescapes.org products page).
But is more really better? Cineform states here that for 4K their codec produces a stream between 30 MByte/s up to 90 MByte/s, depending on the color space. This is far more than an average computer can display without interruptions.
So, if you just plan to play back the movie smoothly, choose a smaller format, as timescapes.org offers for 30" or retina displays.