Paul,
You're correct on all your points, however it runs fine in the background for me when in a model.
Are you running from the Modelbuilder window? That will always appear to run in the foreground.
You need to save the model, close it, and open it as a tool (model tool) for it to run in the background.
You cannot change the setting for foreground/background, or any other properties for system tools. However, like you've noticed, this tool will work in the background. The model itself has a property to allow it to run in the foreground, do you have that one unchecked?