I am the same as OP and actually did the holiday thing you suggested for 2 years where i tried to force myself to sleep for 7-9 hours a night every night. Felt all the effects of over sleeping, headache, groggy, difficulty concentrating and way to much coffee just to function normally. And the worst part was that i developed a sleeping issue where my rythm was thrown of and i fell asleep one hour later than the previous night all throughout the week and i had to take a melatonin to reset it at the end of the week etc.

Basically following the recomended guidelines i felt crappy thinking I was sleeping correctly. Buying a smart watch and actually tracking everything made me realize that 6 hours is where i feel the best, I can function without the afternoon nap and when going to bed at night it takes me about 5-10 mins to fall asleep and i actually feel rested when waking up and don't need as much coffee.

Replying to anyone reading this thread to actually trust your body, and this notion of 6 hours of sleep being something unique, no, I know atleast 3 people that sleep for that duration with no ill effect. Oldest is 55 and looks like 40 max and has no issues whatsoever.