By default Odoo shows only the BOM components at the first level only in the MO. But you could go to the BOM of the product A and view the whole subcomponents by printing the BOM structure.

Manufacturing-->Bill of Materials-->(product A)-->print-->BOM structure

Try to switch bom type from 'normal' to 'kit'. Then u'll see all components add to ur Product A's MO.

Hello TIm,

Let's look at your scenario

Product B --> Component 4
                        Component 5
                        Product C

Product C --> Component 6
                        Component 7

Here if your product C is an assembly of component6 and component7 then in the MO of Product B you would see it to be Component 4to 7 as the components of the product B. But if your product C is not a simple assembly and you are manufacturing it (you are doing some work operations on Component 6 and 7 to produce C) it is quiet logical that the MO of Product B sees the difference between Component 6,7 and Product B and hence the way you see it. 

Thanks

Vishal