Skimming the study I'm not really convinced that the concept of a "golden hour" actually exists. For one it's a cohort study and not a RCT, so reverse causation (ie. people with good sleep sleep at 10-11) can't be ruled out. My guess is that sleeping later than 10-11 is associated with not getting enough sleep (going to bed late = less sleep), whereas sleeping earlier than 10-11 is associated with waking early (eg. waking at 4am so you can work at the bakery at 5am) which is also bad for sleep.
I felt the study was flawed the instant I saw they tied the golden hour to a time. So if I drive a mile to cross the river into the next time zone, I can stay up an extra hour?
This study should have been tied to a concept of sleep rhythm or how long you stay up after you wake each morning. But tying it to such a poor concept of our time(which is tied to time zones which abruptly start/end at specific locations) doesn't give me much faith in the study.