They are for some reason saying they can track things with their colorization, when their colorization is extremely unimpressive as well as the tracking that results from using it.
There is no reason colorization needs to happen to do the tracking anyway. The tracking is unimpressive and now indirect.
This isn't some sort of epiphany they've discovered, they are just reinventing video image segmentation very poorly.
Here are half a dozen examples from a 30 second google search:
https://www.youtube.com/watch?v=juDvLrFQF0U
https://www.youtube.com/watch?v=JYgyDdLf7GQ
https://static.googleusercontent.com/media/research.google.c...
https://perso.liris.cnrs.fr/nicolas.bonneel/InteractiveMulti...
http://files.is.tue.mpg.de/black/papers/TsaiCVPR2016.pdf
https://graphics.ethz.ch/~perazzif/bvs/files/bvs.pdf
The only reason this is news is because it's google and the researchers seem to think they've discovered something. Techniques like this with much better results have been shown at Siggraph for decades.