A lot of people look the same to me (unless I know them). They are just faces in the crowd. Because of this, I'd never swear under oath that I saw a stranger do something. Unless the person had a very distinct scar or birth mark or purple hair, etc. that I could vividly recall... honestly I cannot tell them from the next person.
I think most people are like this, but convince themselves otherwise.
I'm exactly like you. Everyone looks the same to me. But my ex-wife is exactly the opposite. We once walked into a very crowded baseball game at Candlestick park looking for a friend who was somewhere in the crowd (we had no idea where). She found him in less than 30 seconds a quarter of the way around the stadium. I think most people are somewhere in between these two extremes.
I think most people are like this, but convince themselves otherwise.