Can Standard BOM (Structure Item Type = Standard) is part of Model BOM ?

Summary

Can Standard BOM (Structure Item Type = Standard) is part of Model BOM ?

Content

I am creating Assemble-To-Order Model Item Structure (User Item Type = ATO Model - Manufactured) 

Wanted to include sub-assembly (Structure Item Type = Standard) having some purchased components as a part of its structure (consider mandatory components to manufacture the subassembly)

After completing the item structure setup, when I am selecting the ATO Model in sales order, the subassemblies are not appearing in the configurator user interface page, my expectation is, the subassembly item should appear in the configurator page as a mandatory item 

How to setup this in Item structure, please help