The problem with that interpretation is that the emancipation rule does not say “default to the normal rules“, it says that the child is treated as not living with either parent. Example 6 seems instructive here. In example 6, the child lives with parent number two for more than half the nights of the year, but is treated as a qualifying child of parent number one because the child lived with parent number one for more than half the nights of the year before the child turned 18. If the answer was simply to default to the normal rules, the child in example 6 would be the qualifying child of parent number two.
Here, if the child is 19, they turned 18 last year. I agree that it would seem more logical to default to the normal rules when the child turns 18, but it is not clear to me that is the case.
