Swapping the PSU first every single time seems like a good way to sell parts people don't need. A known good unit on the bench tells you right away if the board is even alive, and that takes five minutes. If it posts with your test supply, now you know the old one is the problem and the customer isn't buying anything blind. Doing it the other way around means you might replace a good PSU and still be staring at a dead board. The tech in Tulsa is working backwards from the diagnosis, not toward it.

Ya ever seen a Snap-On break too? Buddy's did mid-u-turn. Quality ain't always the fix.

$9 swing in 3 days? That thing's playing games with people's heads.