Why does SetSchemaMetadata SMT work for $Value but not for $Key in my Kafka Connect connector? - jdbc

Question

I've tried for a few hours to find out why the SetSchemaMetadata SMT works for my value but not for my key even though Kafka Connect detects that the SMT plugin exists for the key (i.e no error). I have also set auto.register.schemas to true to see what schema it generates in the schema registry and the value schema has the correct namespace but the key schema has the default values (i.e. not being set by the SMT).
Here are my connector configs:
'{
"connector.class": "io.confluent.connect.jdbc.JdbcSourceConnector",
"value.converter.schema.registry.url": "http://schema-registry:8081",
"value.converter": "io.confluent.connect.avro.AvroConverter",
"key.converter.schema.registry.url": "http://schema-registry:8081",
"key.converter": "io.confluent.connect.avro.AvroConverter",
"connection.url": "jdbc:postgresql://host.docker.internal:5432/db_name",
"connection.user": "postgres",
"connection.password": "12345",
"table.whitelist": "file",
"mode": "timestamp+incrementing",
"incrementing.column.name": "seq",
"timestamp.column.name": "last_modified_datetime",
"topic.prefix": "jdbc-source-inserted_or_updated_",
"validate.non.null": true,
"timestamp.granularity": "nanos_long",
"poll.interval.ms": "100",
"auto.register.schemas": "true",
"transforms": "AddNamespaceForKey, AddNamespaceForValue, copyFieldToKey",
"transforms.AddNamespaceForKey.type": "org.apache.kafka.connect.transforms.SetSchemaMetadata$Key",
"transforms.AddNamespaceForKey.schema.name": "io.JDBC_Source_Inserted_Or_Updated_File_Key.JDBC_Source_Inserted_Or_Updated_File_Key",
"transforms.AddNamespaceForValue.type": "org.apache.kafka.connect.transforms.SetSchemaMetadata$Value",
"transforms.AddNamespaceForValue.schema.name": "io.JDBC_Source_Inserted_Or_Updated_File_Value.JDBC_Source_Inserted_Or_Updated_File_Value",
"transforms.copyFieldToKey.type":"org.apache.kafka.connect.transforms.ValueToKey",
"transforms.copyFieldToKey.fields":"name",
"errors.log.enable":true,
"errors.log.include.messages":true
}'
Here are the generated schemas:
Key:
{
"fields": [
{
"name": "name",
"type": "string"
}
],
"name": "ConnectDefault",
"namespace": "io.confluent.connect.avro",
"type": "record"
}
Value:
{
"connect.name": "io.JDBC_Source_Inserted_Or_Updated_File_Value.JDBC_Source_Inserted_Or_Updated_File_Value",
"fields": [
{
"name": "seq",
"type": "int"
},
{
"name": "name",
"type": "string"
},
{
"name": "url",
"type": "string"
},
{
"name": "last_modified_datetime",
"type": "long"
},
{
"name": "modified_at",
"type": "long"
},
{
"name": "created_at",
"type": "long"
}
],
"name": "JDBC_Source_Inserted_Or_Updated_File_Value",
"namespace": "io.JDBC_Source_Inserted_Or_Updated_File_Value",
"type": "record"
}