As I grow older, I find the opposite - if I haven't had a physically exhausting day, I need only 6 hours, else max 8 hours. Anything more than this has a negative impact on my mood and health.
I hate articles like these. I sleep 6-7 hours, and it works all right for me. When I sleep 8+ hours, I feel a bit more fresh, but that doesn't really help me do anything more in my day. Id rather have the extra hour to duck around on Reddit or (ideally) do something productive.