They do take that into account and with the latest phones they seem to have prioritized dynamic range (the range between the brightest and darkest parts of the image). However, high dynamic range images can look very flat and if the subject is lit somewhere around the middle of that range it can make them feel darker. If the phone detects a face it will usually push the face to be at least a step or two above the middle, but the XS seems more conservative in how far it will compensate for faces (I can't confirm, don't have one myself). There is also a popular aesthetic in photography that pushes faces to within a step or two of the top brightness and either cuts out the highlights or squashes them. From your comments, it seems that is a look you like.
Photography is subjective, so if that's what you like learn how to achieve that look with your iPhone (the built in exposure slider works well; tap the face/subject you like a push the sun icon upward). My impression is that Apple is tuning their default camera app to look good to professional camera/phone reviewers who will be more impressed by a high native dynamic range and in that regards the XS seems better. If it doesn't work for you, Great! You saved yourself an upgrade.