I am no google fanboy, but I WOULD be surprised to find such a thing. The reason I would be surprised is history and alignment.
Google consistently has bad/non existent customer service
It is famously hard to talk to a google employee when you have a problem
Google has a history of primarily hiring devs
Google knows its bread and butter is legitimate results
Google probably has the largest most experienced anti-SEO team on the earth
Google seems to want to stay out of the press
Google maps reviews are a very major competitive moat against other maps
Google is supported by ads, but AFAIK does not actively seek customers
Google does not do delivery
Google's money maker is getting information, maps is a major input
Maps is a secondary business able to be subsidized by search ad revenue
On the counter side
Inflated reviews/advantaged reviews would make ad customers happy
Selling position is potentially extremely profitable
I just don't see it. It's not googles MO. It's yelps MO. That's why I use google maps as my primary tool for finding whats good.
What I wouldn't be surprised by is google systemically limiting negative reviews. In my experience A yelp 3.5 would be a 4 on google maps. A yelp 1 or 2 would be a 3 on google maps. 4 would be 4.5 on google maps. Google maps numbers are definitely inflated, but once you understand the relative scale it's just as good as pre-corrupt Yelp.
What I wouldn't be surprised by is google systemically limiting negative reviews. In my experience A yelp 3.5 would be a 4 on google maps. A yelp 1 or 2 would be a 3 on google maps. 4 would be 4.5 on google maps. Google maps numbers are definitely inflated, but once you understand the relative scale it's just as good as pre-corrupt Yelp.