Archived versions of the website [1] mention work on machine learning more prominently, as do some of the linked research publications from a few years back [2].
Perhaps the unit was given the name AI initially but its focus later shifted to quantum computing?
Later: A Google blog post from 2021 explains the connection of quantum to AI better than the current website does [3].
[1] https://web.archive.org/web/20201210053216/https://quantumai...
[2] https://scholar.google.com//citations?view_op=view_citation&...
[3] https://blog.google/technology/ai/unveiling-our-new-quantum-...
1. Barren plateaus in quantum neural network training landscapes: https://www.nature.com/articles/s41467-018-07090-4
2. Power of data in quantum machine learning: https://www.nature.com/articles/s41467-021-22539-9
3. Quantum advantage in learning from experiments: https://www.science.org/doi/10.1126/science.abn7293