According to the handbook do have to come to a complete stop. I've not tried it whilst still moving, so don't really know for sure. I just make other traffic wait. If your cars "body language" suggests what you are doing, you'll generally be given time.
I assume you are asking about Mk7's so this next bit will be relevant. What is a bit of a pain is Auto Hold. As soon as you come to a stop, the parking brake comes on. You can't just ease off the brake to roll forwards or backwards a small amount if gravity will allow. You need to press the accelerator to release the Auto Hold, which can result in a lurch forward or backwards. You can switch Auto Hold off, but I didn't know this the first day I had my car, and I was trying to edge out of a downhill junction.