> like an adult who looks 'too young' having their freedoms curtailed because any photos or videos would Look Like CSAM - but I don't think they're common enough harms

It is extremely common in some parts of the world. Age from visual appearance basically doesn't work inter-culturally, with or without AI, and ... there are people amassing something like 1/3 of the world that look like kids until they must retire from all work including use of gas stoves to boil water. Said people just literally look like kids, attracts wrong kinds of the rest 2/3, wrongly reject them if others come over, and gets banned on social media as being underaged, all the time.

edit: I have feeling that the concept of "adults by appearance" might be the case of suspicious discontinuities created by industrial revolution; it is often said that the modern concept of binary child/adults dichotomy is the result of industrialization though the concept of child always existed. For this reason, there might have been selective pressure towards attaining "definitely adult" appearances at younger ages in forerunner regions, and less such pressure at regions that followed it. IMO that makes more sense than assuming people from some regions are obsessed with certain things.