Yes. You are correct about changing in response.
From the documentation: 'schema.data -The field from the server response which contains the data items.'
That is why no 'data' object in response when schema.data not defined in config. (it is working variant)
But when schema.data is defined and response contains object which contains the array - it won't work. There is the reason of the thread :)
P.S. Attached file with Widget config and 2 variants of responses. It contains only the top record, as child won't load in when schema.data is defined.
P.P.S file is here https://www.dropbox.com/s/zeaidvhu9qgojam/settings_data.txt?dl=0