This is more about Revit than Power BI.
Revit distinguishes between area and volume calculations at the object level and material level. The area and volume of Material Quantities refers to the selected material, while the area and volume of parameters refers to the element itself. The calculation method used depends on the category of the element.
https://revitclinic.typepad.com/my_weblog/2009/05/the-difference-between-volume-and-materialvolume.html