https://www.cnet.com/news/apple-to-fix-iphone-xs-selfie-smoothing-with-ios-12-1-beauty-gate/

Now Apple has confirmed that the Smart HDR algorithm wasn't choosing the sharpest image to anchor its HDR merges, resulting in too much loss of texture detail. The Verge earlier reported the update, which involves how HDR modes shoot multiple frames at different exposures and then merge them to create a single frame with an optimized exposure.

The company has tweaked the algorithm in the current beta of iOS 12.1, and separately confirmed to us that a future software update will allow previews of the portrait mode's depth effect before shooting on the iPhone XR.