Hi Revin, I think youtube video is probably older workflow version. The workflow module is updated at 30 September. So the entity relations, context entity and other structures also changed. Please think that point. For the context entity, no more generaization. You should have a context entity(that should not be generalization), 1 WF generalization, 1 or more task generalization entity(s). Workflow is still Beta but most problems are resolved. And at next month it will be GA not Beta anymore. So you can use it.
You can refer to this