I believe the excluding logic only applies on a scene transition. When you switch to an excluded scene, the key goes away, but nothing prevents you from putting it back while still on that scene.Running 0.4.4 and have found the keyer still displays scenes on excluded scenes. Could this be a bug?
If that's what you're seeing, I'd call it a feature and not a bug, because it allows for a near-immediate recovery from a mistaken configuration, that a lot of the audience won't even notice at all.