Why is there a "Goods In Transit" option for material transfer but not when buying from supplier in "Purchase receipt"?

What is a good solution if I want to track which purchases are in transit, e.g. I buy raw materials from a supplier with a purchase order, and then do purchase receipt when it arrives (traditional method without tracking). Do I make stock entry into supplier’s warehouse and then do a separate material transfer with “goods in transit” checked? sounds overcomplicating.