I just noticed this note at the Apple iPhone introductory page that I haven’t seen anyone else mention:
iPhone XR has not been authorized as required by the rules of the Federal Communications Commission. iPhone XR is not, and may not be, offered for sale or lease, or sold or leased, until authorization is obtained.
It still awaits FCC approval. How odd. I wonder if the holdup is bureaucratic or RF-related?
Maybe once the FCC blesses it, Apple will list an unlocked version.