[Edited]
Original problem: I had a policy to Reset Computer Names. I then changed a name in JSS, and as expected, it changed on the Mac. Then I mistakenly believed it change back on its own.
Turns out that I was looking at two different Macs, both with the same name. I started working on one, then stepped away from my desk. While I was away, someone closed the lid of the test Mac I was using, and left their Mac on top, with the lid open.
When I finally noticed this, I set the one on top aside, and checked the one on the bottom. And it did indeed have the correct name!
