Wrong.

Whoever wrote this article pulled the quote out of context.
The clause directly before it reads:

“Google claims no ownership or control over any Content submitted, posted or displayed by you on or through Google services. You or a third party licensor, as appropriate, retain all patent, trademark and copyright to any Content you submit, post or display on or through Google services and you are responsible for protecting those rights, as appropriate.”

Therefore the content author still retains ownership and responsibility.

The quote in question:

“By submitting, posting or displaying Content on or
through Google services which are intended to be available to the members of the public, you grant Google a worldwide, nonexclusive, royalty-free license to reproduce, adapt, modify, publish and distribute such content on Google services for the purpose of displaying, distributing and promoting Google services.”"

Notice that it says “intended to be available to the members of the public”

There is an option (which by default is disabled) to share a particular document and allow access by everyone. I assume that the above clause only applies when this option is enabled, as the document becomes “available to the members of the public”.

It basically gives Google the right to index the document on its search pages, link and cross-reference relevant information, derive some semantic meaning etc… Exactly what you would want if you were to set a document as public.