It took a few months but Facebook finally updated its iOS apps to support the higher resolutions of the larger iPhone XS Max and iPhone XR phones that Apple released last year, allowing Facebook to run on the device's native resolution instead of just increasing the XS-sized iPhone scale, via 9to5Mac.
The upgrade also adds support for the larger screen sizes on newer 11- and 12-inch iPad Pro models released late last year by removing the black bars the app used to display. (Although the usable space of the application is essentially the same.)
Upgraded iPhone apps have a bit more space because of the upgrade. The iPhone XS Max of 2688 x 1242 (3x the effective screen pixels) and the 1792 x 828 iPhone XR screen (2x the pixels) effectively result in a rendered display equivalent to 896 x 414, slightly above the 812 x 375 dimensions. display XS and X.
In related news, Apple revoked Facebook's developer certificate yesterday in response to the social network using these permissions to distribute a tracking application for adults and teens, undermining Facebook's ability to develop new versions of its iOS apps, company to test internally on new hardware.