Only a small number need to know anything, you can order a rocket engine without anyone needed to know how it will be used,same goes for all!the other parts, even the engineers designing parts just need to know how to make it not break.
The people in the control room who high five,whoop and holler have to be in on it, the head engineer,the guy who invented heat shielding,the astronauts,the techs working on the buoyancy lab ie swimming pool....when it's being used for spacewalks. The people who make videos of ships approaching the ISS, which don't seem to give a wide view of said station.
The lower engineers probably have questions which are dismissed or try are too afraid of social or financial consequences for asking questions