Data not processing through parseListData()

I have a list that is working just fine. Gets/Saves to the api nicely. Now I want to add new.

The data coming from the server after save() matches the shape of the data coming from a listAll() but, for save(), parseListData() is not being called.

parseInstanceData() is being called but the parameter being passed is JSON.

If I detect a string, parse the JSON and extract the data element, it all works fine.

I can see no difference. Is there something about save() that follows a different pattern than lists?