There's no way to demonstrate that as one individual, full stop. The burden of proof you require to consider whether a valuable benefit could potentially be derived is unacquirable.

A more interesting test is to measure the difficulty of trying a certain anecdote yourself. How easily can you 'black out' your bedroom and sit, lay, or sleep in it for a 10 hour window at night for 30 days in a row?

If you can do such a test easily, and you are invested in seeing a certain change that you think may result from it, then it does you no material harm to try it. Worst case scenario, you lose sleep for a few days and abort the experiment. Best case scenario, it has a positive impact. The results could be anywhere between those two endpoints.

So, that makes this a 'safe' test to apply to your own personal body system, which is not necessarily applicable to any others.

Anecdotes that require you to alter what you ingest (food, water, supplements, medicines etc) are much riskier, yet people constantly try these out endlessly under the rubric of "diets" without a second thought for the potential of months of damage to their gut biome, muscle mass, hormone levels, and so on. It's been demonstrated by a vast array of people that it's relatively safe to cut out all the sugar from your diet, but you have to make sure you don't let your blood sugar levels fall too low in the process.

Anecdotes that require you to alter your body (e.g. stomach stapling) are even riskier than those, as we have very little experience in this space compared to diets or other non-consumption non-modification approaches.

You are absolutely correct to be suspicious, but consider also the level of suspicion appropriate for the context. "Try blackout curtains for a month at night and charge your phone face down" is a far lower bar to be 'worth a shot' than "Remove all carbs from your diet". And if you see others failing to take this into account, remind them of the inherent level of risk in what they're considering. It's not always about being right or wrong, but instead about e.g. "how much harm could come to me if I try keto diet?".

EDIT: There's very much a personal overtone to these risk assessments as well. My personal mental stability hinges critically on getting enough sleep, so I am unusually wary of anything that messes with sleep, because I need mental stability far more than I need the benefits such an experiment may or may not produce for me.

EDIT: Harness the placebo effect! Believe that what you're trying could help when you try it. If you're doubtful and pessimistic and cynical about something you're trying, be especially careful to focus every day on why you're trying it. Doing so makes it more likely that the placebo effect will enhance your results, and less likely that the nocebo effect will diminish them. This relates directly to a lot of "woo-woo" thinking, but apply my logic above. What's the level of risk of trying a placebo-welcoming approach? You could mislead yourself into thinking something helped when it didn't. Keeping a careful journal about your experiments is an effective treatment for that problem for many folks, and the placebo effect is really powerful. No point in setting aside a useful tool just because it's mind-body.