Unable to register a Custom Converter with MongoDB Connector

We've been looking to implement a custom converter, following the instructions here

We can see in the logs that the converter is picked up from our provided config, and can see any logs we put in the overridden configure method.

However; we can't see any effect on the connector's output, and any logs we put in converterFor are not printed. 

Looking in the connector codebase we can see CustomConverterRegistry (link) which seems ultimately responsible for registering converts against tables - and this only seems to be currently wired into TableSchemaBuilder (link).

The MongoDB connector is newly stable, so we understand if this is WIP / a feature request!

TLDR - Are custom converters currently supported in the mongodb-connector?