Firstly, it’s not “entirely useless”; it just has a slightly lower quality of evidence than a study that was blinded for participants. However, some things are quite difficult to practically blind – and this (not unreasonably) is one of them.
Secondly, you raise lots of interesting hypotheses that might contradict the findings of the study. These would indeed be interesting directions for further similar studies. However, in the meantime, a study (even of moderate evidence quality) is probably more valuable than off-the-cuff hypotheses.
(My low quality n=1 anecdote: i’ve discovered that I am quite light sensitive while sleeping. so measures which minimise ambient light improve my quality of sleep. Whether this is blackout curtains or a sleep mask is more situationally dependent.)
Secondly, you raise lots of interesting hypotheses that might contradict the findings of the study. These would indeed be interesting directions for further similar studies. However, in the meantime, a study (even of moderate evidence quality) is probably more valuable than off-the-cuff hypotheses.
(My low quality n=1 anecdote: i’ve discovered that I am quite light sensitive while sleeping. so measures which minimise ambient light improve my quality of sleep. Whether this is blackout curtains or a sleep mask is more situationally dependent.)