I think part of it is that people back then we're far more likely to not have diverse ancestors- the people in the OP video probably all had parents from the sa

I think part of it is that people back then we're far more likely to not have diverse ancestors- the people in the OP video probably all had parents from the same small town, very different from our modern era. This probably enhanced a lot of distinct body and facial features that have mostly washed away in modern times. However, as an adult you've met enough people to still be able to recognize some of them.