Yes, that's it. I commonly see it when it's an AI opponent sending a single unit, such as an anti tank, to capture one of my empty provinces (assuming that empty province is something other than forest or urban).
If that province is forest or urban, you won't see that anti tank at all.
I don't think I've ever reported it as a bug, it's just something I've accepted about stealth mechanics. It's possible that it's unintended behavior. I'll try to remember to screenshot it next time it happens.
