How can we access the new focal lengths on iPhone 15 models?

The latest iPhone 15 Pro models support additional focal lengths on the main 24mm (1x) lens: 28mm ("1.2x") and 35mm ("1.5x"). These are supposed to use data from the full sensor to achieve optical quality images (i.e. no upscaling), so I would expect these new focal lengths to appear in the secondaryNativeResolutionZoomFactors array, just like the 2x option does. However, the activeFormat.secondaryNativeResolutionZoomFactors property still only reports [2.0] when using the main 1x lens. Is this an oversight, or is there something special (other than setting the zoom factor) we need to do to access the high-quality 28mm and 35mm modes? I'm wary of simply setting 1.2 or 1.5 as the zoom factor, as that isn't truly the ratio between the base 24mm and the virtual focal lengths.