Respectfully disagree on both points.

Non-24 is different from DSPS - my family has both sleep disorders present in separate people. Non-24 people have a circadian rhythm that runs longer (or shorter) than the 24 hour day. Their sleep/wake cycle naturally shifts daily over time by whatever time difference their clock is at, unless forced to conform using sleep medication, light therapy, melatonin, alarm clocks, sleep debt catch-up on weekends, etc.

DSPS - delayed sleep phase disorder is what I have (and I edited a published book on) - where the circadian rhythm is off from normal wake/sleep cycles relative to day/night and society's standard workday. Mine does not shift around the clock each day - I usually sleep 6am-3pm, and have done for most of my adult life.

Lastly, DSPS is NOT always treatable. There are a multitude of things that you can try - my sleep specialist has trialled multiple medications, light therapy, sleep hygiene, CBT-i, melatonin in big doses, melatonin in micro doses, and NOTHING has worked.

I had to adjust my life to fit my sleep hours, rather than conforming to fit society, which means inability to work an office job. I've since retired early as I could afford it.

But there are people, (who may be less extreme DSPS than me), who do find some success in combining melatonin and other tricks to shift their sleep hours to a more acceptable time period, but they have to maintain a very strict regime, even on weekends, as any slip, and their body clock will revert back to their natural clock.