In his review of the iPhone XR Austin Mann writes,
The iPhone XR and XS have the same wide angle lens, a 26mm f/1.8 lens. The iPhone XR uses this 26mm f/1.8 lens for portraits and the iPhone XS uses its telephoto lens (51mm f/2.4) for portraits.
It makes perfect sense to give the focal lengths in 35 mm–equivalent terms, but you need to convert the apertures too for an honest comparison. These cameras are 26 mm f/11 and 52 mm f/21.