Purchasing Order from Material Request are all combined into 1 supplier?

I just evaluating ERPNext and have a simple items setup like following:

Item A - Vendor 1
Item B - Vendor 2
Item C - Vendor 3

All item has re-order level and qty for the same warehouse (called “Raw material”)
Now my material request is created with item A, B, C at the right quantity for the warehouse. Then I go ahead and make purchase order. NOW this is where I don’t understand, the purchase order is created with all 3 items but all to Vendor 1 supplier. What am I missing? I wanted to create purchase order for each vendor (hopefully automatically)

Second question is:
I have : item D
cannot purchase, cannot sell, but set for manufacturing “Allow Production Order” with BOM created using item A, and item B. I want to maintain stock level on this too (like re-order level but for manufacturing) so ie. if below qty 20 then create production order. (or material request first then production order, either way is fine). How to set this up? For now I am having the auto-reorder setup for item D with transfer instead of purchase but nothing is generated.

Thanks much, hope I can get some pointers and maybe use ErpNext for my small home industry.