According to Phonearena, the Galaxy S10 series now has the option to use a telephoto lens in Live Focus mode (portrait mode), finally putting the latest galaxy flagships in line with its predecessors when it comes to photographing human subjects.
Before the unexpected update, the Galaxy S10 and Galaxy S10 Plus will only use the primary camera, or the wide-angle camera (no the ultrawide one), for portrait mode.
The main camera can provide a more consistent image quality in more situations, but its wide-angle lens creates much less lens compression effect that makes any portrait shot look less realistic or intimate depending on your taste.
The telephoto camera, on the other hand, can create the so-called lens compression effect because it has a zoom lens more suitable for portrait shots.
Phonearena can’t pinpoint exactly when the update was made in since it can’t find it in the changelog. But, you can read about how different lenses affect portrait photography here.