Deterministic template export is a way to make the xml content of exported templates constructed in a standard way so that the same template can be diffed and change-managed in traditional cms like git. Before deterministic template export, the xml elements and ids of elements were not built in a standardized way, so changes in the flow generated unpredictable changes to the exported template xml (for example, the xml child element of a processor could change position among all child elements in a way that did not map to changes in the flow). This made change management difficult since deltas in flows represented by a template were not mapped directly to deltas in the template xmls.
This feature was resolved in NiFi 1.0.0:
https://issues.apache.org/jira/browse/NIFI-826