This is not what empirical measurements show. It is referring to a minimum internal benchmark, rather than what actually happens. (source: work there)
If you're getting shadow banned somewhere, it is typically either the site itself or their CDN or bot management providers that is sending you into a challenge loop; hCaptcha doesn't control the behavior in those scenarios.
That’s a 10% fail rate under standard independence assumptions. They wonder why people are freaking out.
For one of my ISPs (carrier grade nat), I get multiple captchas per hour, and frequently find my IP has been shadow banned. This is exclusively while reading the news and using paid accounts in long term good standing.