I also mostly give 5 star reviews, but haven’t experienced this.

For me Google Reviews are a top make or breakpoint when deciding a hotel. I can imagine other people doing the same Hence there is an incentive for hotels to game the system

I recently moved to Phuket and many very mediocre hotels (or plain shabby hotels) get very high ratings (4.5+) and very positive reviews. Hotel competition is cut throat here so hotels definitely have an incentive to game the system.

TLDR Maybe Google notices fraud and is trying to solve in a clunky way