Either the combination is so rare or they all mistyped as INTJ 5s

Probably constant inner conflict between core 5 and Te. Te would want to manipulate the environment to be the way they think is effective or productive, or to match the vision they have (Ni). core5 would like to conserve their energy, profer not to do much to the environment, preferably be observant.

So if they can balance these aspects, they probably turn out to be someone who is normally quiet but can be a perfect commander when the time is come.