When using the HTC Vive with any levels that are streamed in that take a moment to load in will show the waiting room for the Vive while loading. This does not happen on the Oculus that I can see. If the waiting room is not visible during this load add more assets to make the load more significant.
Sample Project package: [Link Removed]
1. Set up a project with at least two levels so one can be streamed in.
2. In the streamed in level add a bunch of assets to make it take a moment to load, 1 second or longer.
3. PIE in VR and load level
Expected: Should not see the waiting room for the HTC Vive
Results: The waiting room appears on streamed in level load if it takes a moment.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-34018 in the post.