I recall this being the case, but I can't find evidence for it when looking recently.
This still being the case could be supported by:
Having Greek culture and language, architecture, etc
Atlantis being a Greek 'myth'
They worship and are seemingly under the domain of classical Greek gods, and their cities are named after these gods
I understand that Atlanteans are their own culture and people, but it seemed that early on they were Greek, or very much Greek inspired/adjacent.
Can anyone confirm or deny?