Joiner preview record view is misleading

To reproduce, create a pipeline that joins data in preview, and run the preview. Navigate to the joiner stage, click preview, then change the view from table view to record view.

This view presents a single record from the left, a single record from the right, and a single output record. This gives the impression that the record displayed from the left joined with the record displayed from the right to generate the output record. However, this is not the case, these records just happen to be the first ones recorded and have no relationship to each other.