They said WORKERS not EMPLOYEES
Sure, Google puts a lot of its revenue to its EMPLOYEES. But most of the WORK is done by the rest of the public giving Google all the content and data via the way the products utilize the searching and driving around and so on.
The claim is not what's internal to Google's business accounting. The claim is that they have externalized almost all the work to the unpaid users of the systems who actually produce the value overall.
(the quote is a tad confusing because they said "employer's revenues", that seems like an error in speaking/writing; the next part makes it clear what they are aiming to say)
> paid labour performs only a fraction of the work that Big Tech benefits from