prob tech and UX issue. FaceID can't do side ways, and people opens side ways half the time. Maybe there are also functions unlockable wihtout clamshell opening. can't put 5 faceID on each side and facing every which way.

While at launch Face ID did not work in landscape, it does now. I can unlock my phone with my face in both landscape and portrait, although I guess not upside down? That might only be because I’m on an iPhone though. iPads might be more flexible.