What differed between Acrobat X & Acrobat Pro 2024 as far as using FDFs?

Hi, we have a propriatry insurance program that prints policy forms made from PDF templates, using FDF specifications to merge policy specific data into various forms. 

The program was using FDF 1.3 specifications and Acrobat X standard to accomplish this and all worked fine. We're not doing anything really fancy, BTW,  just adding a signature line to certain forms as well as filling in specific form fields. We are, however, creating multi page documents and multi document "policy" booklets, sometimes in a batch were we prepare policy booklets for mulitiple customers in one big process. 

Now that we are trying to move to the latest version of Acrobat (Pro), however, we've run into issues.  It seems that the /Pages <<>> and the /Templates <<>> arrays tags are no longer recognized correctly. I've gotting an "Expected a dict object" error for an FDF with no fields and a single /Pages specification and building FDFs without /Pages & /Templates appears to restrict us from automating the building of multi-form policy booklets.