I'm starting to suspect we're using two different definitions of "rule of law". Here are a couple of excerpts from the wikipedia article about it that explain how I'm using it:
Formalists hold that the law must be prospective, well-known, and have characteristics of generality, equality, and certainty. ...
According to the functional view, a society in which government officers have a great deal of discretion has a low degree of "rule of law", whereas a society in which government officers have little discretion has a high degree of "rule of law". ... ... according to political science professor Li Shuguang: "The difference....is that, under the rule of law, the law is preeminent and can serve as a check against the abuse of power. Under rule by law, the law is a mere tool for a government, that suppresses in a legalistic fashion."
"Discretionary enforcement" of the law in the US is limited to situations like speeding, or marijuana possession. Due to the (explicit and intentional) separation of roles of police, prosecutor and judiciary, it's hard to prevent enforcement of serious offenses without a grand conspiracy, and even then, the victim can appeal to the FBI and bring another layer of oversight to bear on the problem. It's similarly hard to escape being prosecuted for something serious. In China you have one Party overseeing everything.
Further, understanding a system, and believing it to be applied consistently, is not a requirement for a rule of law. It just means your citizens and your system of justice and equity have grown accustomed to each other. For you, "don't piss off the Party" might be a perfectly understandable rule, and punishment for pissing off the party may be quite consistently metered, but that isn't what rule of law means.