Chinese alchemists were just a whole different level of charlatan, man. "Severe heavy metal poisoning symptoms? Come on bro that is just the immortality entering your body haha! you are getting stronger just one more dose and you can fly haha! you did pay me to make you an immortal right?"

It's not that quackery is unique. It's that they did this specific thing for millennia with emperors who should've known better, like those who punished the ones who killed their dads.