Solution : https://service.sap.com/sap/support/notes/134488 (SAP Service marketplace login required)
Key words : 
additional key words phantom assembly, reference field csdata-xfeld, process order/production order, attached source code, import parameter svwvo, set flag 'optional', bom explosion works, lower-level components, process order, phantom assembly
Related Notes : 
       
| 396441 | |
| 305263 | |
| 138789 | BOM explosion with different usages | 
| 135480 | Explosion of phantom assemblies in order and plan |