This part is moot since the Chruch in this case accurately defines her as a Catholic because she considers herself a Catholic.
What it does do is shoot down the notion you brought up earlier which suggests that because there are children being baptized that their parents must also be believers (which in this case is only 50% accurate).
But they are believers, what else can they be if they baptise their children in the Catholic faith - why bother doing it at all? Do protestants or Muslims baptise their kids as Catholics?
It makes absolutely no sense. The morality aspect will not be applicable, if the kids are not sent to Catholic schools and/or brought up with the faith. The fact Catholicism instills moral values is then a moot point unless Catholic values are instilled into the children, in the first place, which can only be through the parents and/or through schooling.
Why baptise your children into a religion that you do not believe in at all.
Right, some of them may return. Some of them will leave and gladly not look back. As you said yourself who’s to know what will happen in 5-10 years, yet you seem to suggest that by default when counting active members (not just those baptized) that we should default on the idea that they will return.
What difference does it make - and it is impossible to register those that return especially in this day and age with people moving for marriage, college, work etc… very few people remain in the town they were born in. So if a later date ex-Catholics return they will be most likely at a completely new parish and will not register. By registering the number of baptisms it gives an actual, accurate number of Catholics - especially within the Church’s eyes, which is what the statistic is for.
From what I’ve read the ones who left and never returned exceed the ones who have returned, yet as I noted you want to continue treating them as active members because some of them
might return. You would not do the same for those who left a Protestant faith for the Catholic one, and hold out the possibility of them returning to their Protestant fatih.
From what I’ve read it’s completely the opposite. The Pew surveys only state a point in time. IF they can follow the respondents until death, only then can a true statistic be garnered. I’ve known numerous cradle Catholics that have nothing to do with their faith through life, although they still would maintain they are Catholic

- but return when they’re on their last legs

- so it ain’t over until the fat lady sings.
It is difficult, I agree. But the Church actually made it more difficult by enacting Omnium in mentem to prevent such useful information from making it into the Church’s records.
And just because it’s difficult doesn’t mean that one shouldn’t make a best effort to get accurate information, and more importantly not portray these many many many people falsely.