[timv]

The issue doesn't appear to be "pay" but conditions.

From the decision (linked 2 up)

At all material times, Respondents Cognizant and Google have codetermined the essential terms and conditions of employment of employees employed at the E. Parmer Lane facility and have been joint employers.

(2nd to last paragraph of "Findings of Fact > Jurisdiction")

The original article (the register) quotes a union member

Google and Cognizant have proceeded to make unilateral changes to our working conditions such as a forced return to office, removal of sick pay during a global pandemic, and the implementation of a 'Clean Room' policy that bars us from having our phones, paper, or pens in our office, without bargaining with our union.

The line of reasoning seems to be something like:

- There are decisions that Google is making that, if the workers were employees, would need to be negotiated with the union.

- Google is making those decisions with application to the contractors as well as their direct employees

- Consequently, for the purposes of union negotiation, Google is a joint employer (alongside Cognizant) of the contractors because it is making decisions that affect the workers and ought to be negotiated with a union.

If that is the argument, it seems fair to me.

If Google wants to make decisions about the employment conditions of contractors then it needs to accept that it is an "employer" of those workers. Alternatively it can decide not to make decisions about their conditions and leave all of that to Cognizant - but in that case it cannot enforce those policies on the workers until after Cognizant has negotiated with the union and reached an agreement about the the workers conditions. Google would have to make sure that every workplace policy that they wished to have applied to the contractors was handled as a contractual arrangement between Google and Cognizant, not an employment arrangement.