Since measuring equipment has capacity to measure small changes, it probably measures differently, but is it audible?
And, as Richard Pierce, a well regarded speaker person, after speakers sit, it returns to its original numbers or very close. So, it is a moving, dynamic target.
The real question is audibility. Who can hear it under bias controlled condition? Anyone on the planet? If not, It has no meaning the the listener, just another audio hype.
ps. Tom Nousaine measured drivers as you indicated, actually he measured it after 150 hrs:
Nousaine, Tom, 'Breaking Wind,' Car Stereo Review, Jan/Feb 1997, pg 90-94.
Nousaine, Tom 'Test Report: Dynaudio MW 190, 12" Subwoofer,' Car Stereo Review, Oct 1997, pg 83-88.
Some parameters went up, others went down, yet, it was not audible.