You seem to have implied sleeping long offers productivity. Might it be the case others are equally productive at the recommended 8 hours? Might it be the case that you need two hours extra sleep per night to get where everyone else is cognitively with eight hours sleep? Because if that is the case then you are losing time, productive time, and may in fact be losing some of your life, depending on how one views it. You may be sleeping away 8.33% of your life needlessly. If that isn't worth it to you to save then happy dreaming to you.
Fair enough (and I don't see why you got flagged, as you contribute to the discussion; I upvoted all your comments, I hope ot helps)
Others could be as productive as me in 8h or 6h or even less for all I know. I just have not met such people. Most people I know sleep little and are by my own standards not productive (I mean I would never hire them, sorry if it is rude)
Your other point also makes a lots of sense: I may be losing 2h per day due to sleep. OTOH, I generally wake up by 11am, am done with breakfast and shower by 1 or 2pm, and start working for real by 4pm, so I'm already wasting time by myself :-)
But in a few hours of highly productive work, I often achieve my goals. When I don't, I very quickly find another way to get the results, because IT NEEDS TO WORK NOW!
Lazyness, impatience and hubris are my best qualities!
I think the point the poster was making is that it's possible the issue is with the quality of your sleep. Someone getting a lower quality of sleep will need more hours of total sleep every day to be as well-rested as someone with a higher quality but fewer hours of sleep.
Of course, that's not necessarily the case. Everyone has a different genetic need for and predisposition to sleep.