Actually, the woman on the right looks a lot older than 50 + ~13, unless the point Bing AI is trying to make is that aging process is going to be faster in the future (never mind that it is supposed to be quite the contrary, and goes back to the point of AI generating based on existing content). But yes, it does seem to be distinguishing between the prompt for a human (as a species) in 50 years vs. a (specific) teenager in 50 years.