The difference between Typhoon DAs is that they were pure development, built many years before any production aircraft and any production contract.
The Instrumented Production Aircraft (IPAs) were more aligned and BT005 came straight off the BAES production line direct to the flight test dept for a few years before being upgraded/converted and given back to RAF. Although I am unsure how instrumented this was, if any. I was under the assumption F35 doesn't have the same development plan and uses something equivalent to the IPAs?
BAES and partners used the DA program to understand and fix many problems prior to production which helped enormously.