How do you explain "This is not an officially supported Google product."?

https://github.com/googleworkspace/cli

There are plenty of such projects with similar disclaimers under Google's own /google/ organization. To give a few examples:

https://github.com/google/python-fire / https://github.com/google/pytype/blob/main/docs/index.md / https://github.com/google/dopamine / https://github.com/google/go-tika

Also plenty of official Google organizations that are not /google/ , but have official projects.

https://github.com/googleapis/googleapis/discussions/865 / https://github.com/google-research/big_vision / you can find plenty more

I wouldn't read too much into it, since it can mean virtually anything.