Almost zero chance it's that. They don't need to pay people to do it when they know people are more than willing to do it for free due to a lifetime of capitalist indoctrination.
They may not need to, but that doesn't mean they aren't. There seems to be an inverse relationship between wealth and skin thickness, which would make that of Google translucent..
Eh, I think the consequences if they got caught out doing this would far outweigh the tiny benefits they get from it. Not to mention how incredibly easy it would be to get caught.
Compare to other levers they could pull, like a small change in the YouTube algorithm to favour anti-union content. Which would have a far more wide-reaching impact, and would be far harder to prove causation.