Many thanks to all for your valuable input and patience with this.
The development team replied:
The ConnectTo API was the barebone connection only. It does not have the rich capability of the UI. It has been a known issue for a long time. We will take this as an API feature request to be prioritized.
Checking the forum discussion, it seems the customer found some workaround to move forward; not sure how that impacts the priority. The underlying issue is real, valid and requires a fair amount of effort. Ideally, we like the UI and API user calling into the same method. Unfortunately, that is not the case of ConnectTo at this point.
We may explore the possibility of putting a wrapper and validation around the internal method RbsEditorUtils::RbsConnectionElementPickEditorSolution to expose that to the API. We logged a development ticket REVIT-205160 for this under MEP Mechanical Routing Solutions.