Please make it so users can modify their orientation for view. There are people who are bedbound or just prefer to lie down. A few, like Virtual Desktop and Tripp, accommodate different body positions and it is very helpful.
It’s simple to do so FB must not be doing it for a reason. Whatever that reason it, please do it anyway! If it causes problems for regular people then put in the accessibility options. But please please let us do this.
Facebook, can you not understand what a life changer VR can be for someone who is stuck in a bed for the rest of their lives??