The difference between "Official" and "Custom" device status was S-Health.
I was freaking out over being unable to get my S5 to show as "Official" in its device status (wanted to update, but was told I couldn't) .Out of paranoia, I copied over all my Downloads to my SD card and removed it, deleted any root apps and even cleaned it up using SuperSU. And I rebooted a lot. After I finished, I still saw
Device Status: Custom
Then, I remembered the S-Health bug. Since i like S-Health, I had switched it over recently from being a System app to being a User one (because S-Health on a rooted device was, well, broken). So I re-rooted with SuperSU, then re-opened Android Tuner Free and moved S-Health back from being a User app to being a System one again.
Device Status: Official
I didn't even have to unroot, remove the SU app, or reboot it; I just checked back in Settings and it was "fixed."