I assume this call is on the entity rather than the table to facilitate the lookup in SqlProvisioner? Does the find() on $SrcTable in syncReferenceData() correctly populate url even though it's a virtual field? (If not, we'll need to add the callback back in, and then this call could move to the Table to simplify the lookup in TAndCAgreement.php.)

I assume this call is on the entity rather than the table to facilitate the lookup in SqlProvisioner?

Yes, placing _getUrl() on the TermsAndConditions entity encapsulates the fallback logic directly on the data object, allowing $tc->url to resolve automatically across the entire codebase, including SqlProvisioner, TAndCAgreement, REST APIs, and templates, without requiring callers to instantiate or query a table helper.

Does the find() on $SrcTable in syncReferenceData() correctly populate url even though it's a virtual field? (If not, we'll need to add the callback back in, and then this call could move to the Table to simplify the lookup in TAndCAgreement.php.)

Yes, because url is a physical database column, CakePHP tracks it in the entity's visible fields upon hydration from $SrcTable->find(), and $r->toArray() automatically invokes _getUrl(?string $url) during serialization to populate the resolved Mostly Static Page URL into the target record without needing the processTAndC callback.