ArcGIS Pro is great when manually adding a one-to-many join: it duplicates the records which can then be exported to a new feature class. However, I just added "Add join" to my model, followed by Export features, and it does not work. This is the part of the model:
Looking at the intermediate data, Summarize Within works fine but there is no join and the exported feature class only shows Null values apart from ObjectID and Shape fields.
I have double-checked the "Add join" parameters and see nothing wrong there, so I just wanted to hear from others - have you successfully incorporated "Add join" with a one-to-many join in the model builder? Is this supposed to work? Is this a known bug?
Have you tried forcing the preconditions?