I agree that strong emotion on both sides tends towards reviews. However that’s not quite the same with Amazon star rankings that are prompted and take a single click.
Despite that I also work with Customer Satisfaction Surveys and we see 3 star equivalents a lot. There are lots of 3 star reviews on Amazon for other products. Just not TTRPG.
The 4e PHB has 10%

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️ rating and 12%

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️ star. These people aren’t saying they hate 4e. Only 2% gave it

️. It’s not true to say people don’t give middle ground reviews.