Do we need to assign a resource to every item with a work definition for planning purposes?

We have the rule to assign a resource (if needed, no cost) to any Item that has a work definition, based on previous documentations on Supply Planning Cloud. If no resource was assigned to an item, MRP and material explosion in general did not work from that level and below.

Looks like this is no longer necessary. Wondering if this changed over time. Our current version is 26A and we had this for at least a couple of years.

Is this still a valid configuration rule that affects planning? We have common scenarios where an item with a work definition does not need resources, particularly Phantom Items; "MRP" Resources are artificially assigned to comply with this and knowing if th is is no longer needed would streamline our MFG BOM and work definition maintenance.