I was thinking it would only be the XS line. Wasn’t that the reason for adding antenna lines and messing up the symmetry on the bottom?
Yeah, some articles initially said LTE Advanced devices, but digging in, it looks like AT&T's features and usage lines up more with LTE Advanced Pro (what a mouthful): https://en.wikipedia.org/wiki/LTE_Advanced_Pro
(So yeah, XS/XS Max would be my guess)