There might be applications and contexts if you consider “passive testing” as the same as “observing the system” and “field studies”. For instance it might be passive testing when you do user experience (UX/UI) testing by observing a user interacting with the system, but you cannot yourself interact with the system. In that context passive testing becomes similar to behavioral observations popular among social and anthropological sciences.
Interestingly this trends towards not so much getting information about the system, but about the people using the system.