I'd say it's a dangerous step to assume that once you have completed the flight envelope expansion portion of a test/cert programme, that the balance of the flying required is somehow not 'proper flight testing'.
Until ALL the cert testing is completed, and the TC issued, you're in an experimental aircraft; it doesn't have the benefit of much air time, so anything could go wrong at any time. Every flight should be regarded as a test flight until AT LEAST the TC is achieved; even after that, if the aircraft remains on post-cert test activities it's still the same 'first off the line' aircraft, probably isn't fully conforming, and still more hazardous than a regular production type.
You also, realistically, can't simply test the flight characteristics first and only do avionics and systems once the flight characteristics are known. There's always scheduling constraints, and you inevitably end up with a mixed sequence. Obviously, there's still a sequence you have to follow, but it's entirely possible that, say, icing trials, or performance tests, will come after a good part of the equipment tests are done.