Dear Hiba Sharif,
I check routine copy control from Delivery type LF to Billing type IV and I see that beside especial Copying requirements 015 (for header) and 014 (for item), there are no different with configuration copy control from Delivery type LF to Billing type F2.
So I think that beside routine which select from Copy control, system also base on Sales document category ( 5 - Inter-company invoice; U - Pro forma invoice) to progress copy process.
Conclusion, I think we need enhance more indeed in system or choose another work around solution like outputting printout pro forma invoice from SO data,...
Manh Tuan.