"I'll be doing it for them at eighteen"
Here's the fear that keeps the standard high. If you pack the bag, you'll always pack the bag. If you make the list, you'll be making it at university. Help now is help forever, and the standard is the only thing standing between your child and a lifetime of being done for.
Munakata's third transition is the answer to this, and it's the most hopeful thing in the research. Children move from relying on signals in the environment to being self-directed. The move is developmental. It happens. What the signals do, in the meantime, isn't prevent it. They're the thing being moved from. A child who's cued at nine isn't a child being held back from self-direction. They're a child at the stage before it, using the cues that the stage requires, and the self-direction comes as the underlying functions grow, which Best and Miller say they do throughout adolescence.
So the picture of an eighteen-year-old still being packed for by a parent isn't the result of packing at nine. In my experience it's the result of two other things. Either the parent went on doing everything long after the child could do it themselves, which is a failure of the handover in chapter 20 and not a consequence of having helped. Or the child was never helped, was labelled instead, and arrived at eighteen with a belief that they're the sort of person who can't, which is chapter 17's cost, and which does more to produce a helpless adult than any amount of packed bags.
The handover is the method, and it works like this. With you at first, then cued, then alone, one task at a time, moving each one along when it's been managed at the current step for a few weeks. The list by the door at nine becomes a list the child writes at eleven, becomes a habit of checking the bag at thirteen, becomes nothing visible at sixteen, because it's in their head now, where the shelf has grown to hold it. That's not doing it for them at eighteen. It's the only route I know to their doing it for themselves, and the standard, held at adult height from nine, isn't a route at all. It's a place you've asked them to be and called them names for not reaching.
You won't be packing the bag at eighteen. You'll have handed it over at twelve, and you'll only have been able to because you were packing it with them at nine.