Of course!
I made a new forum to test out the functionality. I then made a test user with the participant forum role and had that user make a topic. After that I switched back over to the admin account, approved the topic, and attempted to add a reply which had to be approved before being posted.
It might help if I also better explain what the client is trying to accomplish.
They want to lock down all topics to replies until the topic gets approved, after which all participants can reply w/o moderation and the public can view the topic and all replies.
