Self reported data isn't good enough for this, there are plenty of ways to gather data to test sleep quality that would make a study about this worthwhile- helping with insomnia is one thing, but actually improving sleep quality is an entire other thing. Not that I wouldn't love a strain that actually improved my quality of sleep!! But as a long term daily user who also uses sleep monitoring devices, cannabis definitely hasn't improved my sleep quality 😭
I think you are right, I read something saying that. In fact this is the reason it's harder for a lot of people to wake up in the morning because you need more sleep to compensate. Also from personal experience, when I smoke for a lot of days straight, the first nights I sleep sober are always weird : deep sleeps are way more intense and my dreams are so much more vivid it is almost scary.