I reached out to FA/PA and got this clarifying response:

Marketing Requirements are always derived from user stories and are never intended to live without the context of associated marketing requirements.
These MRs are children of US 4855 which describes the intent of the unidirectional connection and US5319 which describes the commissioning of a connection.

The relevant marketing requirements under here are:
5292: The unidirectional C2C connection shall apply to a single pub dataset (with no matching requirement for sub dataset, although I note that the TWG has made this technically possible)
5293: The unidirectional C2C connection shall be initiated by the Sub controller
5301: A controller vendor shall implement support for reception of at least one unidirectional connection
5302: A controller vendor shall implement support for initiation of at least one unidirectional connection
5307: Conformance test shall validate a controller’s ability to publish
5308: Conformance testing shall validate a controller’s ability to subscribe
There had previously been some confusion about interoperability risks in components that had no ability to initiate a connection. This was resolved by making the connection manager mandatory in the controller profile while allowing (but not making mandatory) the support of an external connection manager.

Perhaps the most salient information comes from MR-5293 where it states "C2C connection shall be initiated by the Sub controller". A subscribing controller is going to receive data for use in its program. It only makes sense that it would know what that data is, how it wants it, and when to go get it.

Tests should be written for the following:
Validate a controller’s ability to publish (5307) OutputData on a unidirectional connection initiated by another controller (5301).
Validate a controller’s ability to subscribe (5308) to InputData on a unidirectional connection initiated by itself (5302)(5293).
This is what has been required. Anything other combinations of support would be optional.

We discussed during today's AWG meeting and determined that UAFX IFunctionalEntity InputData and UAFX IFunctionalEntity OutputData should both be made optional in the controller profile.
This will allow for applications that only support inputs or outputs and correctly drive the conditional testing of the right combinations made in the requirements shown above.

Changed the InputData and OutputData CUs from Optional=FALSE to Optional=TRUE in the UAFX Controller 2024 Profile.