can atlas also generate 3D without pose information attached to the input images?

Yes, as long as the input images are "poseable" -- if they were taken in the same space they need to have some overlap, where the same object or part of the scene is visible in multiple views so the pose can be predicted.

You can also manually position the input images in 3D space to create scenes generatively; we show examples of this in the "generating with spatial context" section