Record Sync Filter Fails when using Sync Records smart service for filter on relationship value

We are updating an old application from CDT/DSE to Record Types.  In a certain process a parent record is written, then child records are generated with foreign key values for the parent and they are written.  This is all done with the existing CDTs and DSEs.  The data propagates to the new Record Types as desired.

However, we have a business critical sync filter on the Child record type that is intended to prevent certain statuses on the parent record from allowing anyone to find related children.  This filter is not being applied by the data propagation feature.  

Believing that perhaps it was a syncing issue, I tried using the Sync Records smart service in various combinations with both the Parent and Child records.  Syncing the Child records, then the Parent, then I tried the Parent first and then the Child.  Nothing worked.

It is my belief, that the Sync Records smart service is not sourcing the Related record when applying the sync filter.  

As a workaround, we have applied Record Level security for the affected records, and this appears to be working.

How can I ensure that the Sync Records smart service correctly applies the Sync Filter?