A simple way of thinking about this is the province makes a law about workers compensation called the WCB Act. The provincial WCB / WSIB / Worksafe look at the Act and create policies. These policies are what are used in order for workers comp to make a decision on a claim.
While the Act does carry information that could be used in an appeal, the policy answers specific questions. In my experience, I have become an expert in understanding and interpreting the WCB policies. In doing so, I have an understanding of how WCB will makes it’s decisions.
When you get to higher levels of appeals, the discussion will usually be around the interpretation of the WCB policies vs. the WCB Act.