Ok, that's what I thought too.
Thanks guys, I rendered a few clips so you can see what I'm trying to describe.
In clips that just have a static tilt offset, the letterbox will move between clips. The ones with automation, the letterbox will move with the automation.
I'm still learning so I wasn't sure if I was just making a mistake. Perhaps I ran into a bug here. At least I don't remember seeing this happen in Resolve 10 Lite.