Unable to see Project Strategic Impact Drivers in Project Online OData Feed

I am using both Power BI Desktop & Power BI Pro to analyse project-related information maintained in Project Online using PWA _api/ProjectData ODATA feed. I am able to view and load PrioritizationDrivers, Prioritizations, PortfolioAnalyses, PortfolioAnalysisProjects, BusinessDrivers, BusinessDriverDepartments and PrioritizationDriverRelations data as well as Projects data.

I would like to analyse the mapping of Projects directly to Business Drivers as captured in the Project Strategic Impact Page but this data is not visible in any tables viewable in the ODATA feed. I feel there is a missing associative data table between BusinessDrivers and Projects.

Can anyone advise how I may be able to access this Project Online data In PowerBI?