Why is success date this mysterious field that cannot be viewed or exported? It is great that you can change it using a flow step, but for those individuals who like going into analytics and actually confirming that your data is flowing properly into RCA, there is nothing you can do but assume your multi-touch attribution is working as expected.
There is no way to audit your Program attribution easily.
Of course you can create a custom field that updates every time a program status changes to success, but once a lead is a member of two programs, that field becomes garbage.
If you can view and export the field member date, I think you should be able to view and export the field success date to ensure your RCA analytics is correct.