Your own link contains this: It's important to note that the expectation of privacy discussed here means something different than when it's used in connection

Your own link contains this: It's important to note that the expectation of privacy discussed here means something different than when it's used in connection with searches by persons acting on behalf of a city, state, or federal government. So how is it relevant? They clearly say the definition discussed is between private individuals, not the state and individuals.