Hi,
I agree with you, that is a bug. I fixed it in my copy today so it will be fixed in the next release.. I added an IsPublished field, but I also enforced not showing posts with a future publish date even if they are flagged as published.
So basically a post is now considered a draft if it either has the IsPublished flag set to false or if it has a future start date. The default is for IsPublished to be true. This way users who use tools like Windows Live Writer can make posts with future publish dates without having to worry about the bit flag which is not available from the Live Writer UI.
Best,
Joe