why do you think "this is not how it works"? i may have only an anecdote and some reasoning to support my point of view, but you have squat to support yours.
And why do I think that this is not how it works? Well, it hasn't been so, when I was 5, not when I was 7, not when I was 14, not at 20, nor at 30. It isn't so in my 50s. It's currently 2:50 a.m. local and there's no chance, I can get any sleep for another few hours. (So I'm going to do some work, until any of the early birds manage to show up.)
You're the one in this thread with the blanket statements that everyone can train themselves to be a morning person along with the blanket statements about how flexible or inflexible everyone's chronotypes are.
Go look in a mirror right now and figure out how much of a hypocrite you are.
Maybe you can't see it because you need better rest.