Scenario is very simple

1 - First I send a PUT:
put /config/service-function:service-functions/service-function/nat44-1/

I can get the data created with:

change.getUpdatedConfigurationData() or
change.getUpdatedConfigurationSubtree()

2 - I send a second PUT

put /config/service-function:service-functions/service-function/nat44-2/

I get a callback but existing API can tell me the created data in a DataObject. They all return NULL.

I can see from a GET that both service-functions were created in the datastore.