Production version without rounting

Dear Expert ;

What I know is that the production version is a combination between a specific bom with a specific routing .

and I thought that I cant create a PV without specifying a routing which is not the case because sap allow me to create a PV without a routing.

so my question is what is the concept behind allowing creation of PV without routing ?.

I found in the community topics that in this case the system will use the setting maintained in OPL8, but actually there is no routing for my material so how I can create PV with only a bom?

Thank you