Material pull as assembly revision box greyed out

In the engineering workbench, when a material is marked as “Pull as assembly”, the ECORev.RevisionNum field is greyed out. Is it possible to select a different revision to use?

I am building a configurator and there are some bill of material lines within a subassembly I would like to switch to template placeholders for use within a Template BOM.

E10 version: 10.1.600.7