According to your source, milk and other dairy foods are poor sources of Vitamin D. Its only after fortification with added Vitamin D that they become good sour

According to your source, milk and other dairy foods are poor sources of Vitamin D. Its only after fortification with added Vitamin D that they become good sources. So, I dont see any reason to choose dairy over any other source of supplementary Vitamin D (yes, dairy has calcium, but so do many other foods).