Sort-of. Because In Anglo world "aa" is "ä". Even ChatGPT thinks that it ok to use "AA" when making a Finnish morse generator.
In hindsight Maaori is not so bad. Some American Indian writing systems are just pronunciation quides for Anglos (or French). I tried to study Haida some 30 years ago, but it was too complex and miserable, because there was no actual audio clips available at that time.
ChatGPT doesn't think, and I fail to see how it is in any way relevant to the discussion.
Marking a long vowel with a macron has a long heritage, dating back to Ancient Greece at least. Yes, some other writing systems, such as Greenlandic, use a double vowel.
Finnish seems to use ä, ö and å as independent letters, rather like Swedish and Danish, unlike German, were ä, ö and ü are regarded as a, o and u with a diacritical mark. These do not seem to be symbols which mark vowel length.
I don't know Māori, but the Wikipedia page gives the alphabetical order for the language and does not list the long vowels separately, so I assume that, as with German or French, they're regarded as the standard letters with a diacritic mark added.
They are indeed standard letters with diacritics added - but macrons are the only diacritical marks used for Māori. Some people do use double vowels but it's less common than using macrons.
In hindsight Maaori is not so bad. Some American Indian writing systems are just pronunciation quides for Anglos (or French). I tried to study Haida some 30 years ago, but it was too complex and miserable, because there was no actual audio clips available at that time.