Why does wet sanding by hand still beat the DA for me after 12 years

Last Tuesday I was finishing a rear quarter panel on a silver Camry and reached for the DA like always. The clear had a couple of small dust nibs, so I switched to 1500 grit by hand with a soft block and a spray bottle. Took me about 20 extra minutes, but the finish came out flatter than anything the DA has given me in that spot. My old mentor at the shop on Vine Street used to say the DA hides your mistakes and your hand shows them to you. I tested that on a scrap panel a month ago with some cheap base coat and he was right. Curious if anyone else keeps a hand sanding step in their flow or if I am just slow and stubborn.