Break in is real for most speaker driver suspensions. After initial manufacturer the suspension is a bit hard and stiff requiring a few bonds to be broken to settle on the designed stiffness. This typically takes a few minutes at full deflection to achieve. An hour is plenty with longer normally being suggested for reasons that are not to do with the mechanical properties of the drivers.

Driver manufacturers supplying matched drivers will break them in before testing and matching hence this is likely to be the most reliable procedure to follow. Of course most premium speakers that place significance on technical performance are likely to have broken in their drivers so that checking the technical performance of the speaker is within tolerances after manufacture is reliable. It might be possible to include a factor for suspension loosening but it would be less reliable in terms of quality control.