I was wondering the same but then I realized this isn't a linux distro - just the linux version of a video editing tool.
It should be noted that LightWorks is a professional grade tool that has been in development for a long time. It has a lot of features that are shared with some pretty expensive high end packages and has innovated several common features that are standard among packages now days.
I would suggest that whilst it can be used for grading, its an editing tool primarily.
Baselight(and davinci resolve) on the other hand is a grading tool, however it can be used as an editor.
I think in this case "professional[-]grade" refers to the quality of the software, not color grading. Isn't English fun?
this was exactly my interpretation. "Lightworks Linux", rather than "Lightworks for Linux".