I'm about to deploy LBP and currently researching for best practices and came across your thread.
I know it's an old thread but based on my experience, what you are experiencing is normal when using Microsoft Office or possibly any apps. The printer will stick to the one it was assigned to when you opened the program. You don't need LBP for that.
Without LBP, it will be the same thing.
You are correct, the only workaround is to close and reopen the app.
Hope that helps.