This does seem to use AI or at least not use the "human workers" method.
Going to the Google SSO page for their signin flow and clicking on the blue domain name for their app, the Google auth page shows the email of the GCP account that started the auth project, which in this case is jaewany@gmail.com
Looking that up on Google shows that it corresponds to Jaewan Yun.
Looking him up on GitHub gives you his profile which contains some captcha solver extension code for this very website and also many TensorFlow-related things.
His personal website[1] also lists the solver under "My Products"