The Routes on product B, C, D, E and F determine how THOSE products are procured. 

The Route on product A determines how THAT product is procured.

If you want a Manufacturing Order created for Product A, set the Route on Product A to Manufacture.  This doesn't prevent you from creating a Purchase Order for Product A if you occasionally purchase it (make or buy scenario).

You don't need Routes on the other Products unless you want Odoo to try to procure them (either create a draft Purchase Order - use the Buy Route; or create a Manufacturing order - use the Manufacture Route).  If you manufacture products B, C, D and E, then mark them as Manufacture also - but make sure you have a Bill of Materials configured for each of them. If you purchase products B, C, D and E, then mark then as BUY - but make sure you have a Vendor configured for each of them.  If these are low value items you procure outside of Odoo and don't count during a Cycle Count, mark them as Consumables and Odoo will never try to manufacture or purchase them.

You should be choosing BUY or MANUFACTURE, not both.