Al the reason for the high volume is lower volume hides issues. Buzzes or resonances have a habit of appearing when the speaker is pushed.Agree on doing the sweep , but 85 db is pretty loud for 1K and arnt those Speakers typically 78db sensitivity , i would suggest 80db which is pretty loud enough and do the sweep..
The other reason is if you cal the volume at 85DB at 1K and accidentally slip the slider to 10Hz you won't cause massive bass panel excursions that are enough to damage the panel.