I agree there are four functions in the functional stack, but Celebrity Types calls the inferior function "repressed." Confusingly, that site upholds the concept of function pairs.
In this way I do somewhat disagree with Jung believing the 3 remaining processes were of opposite orientation than the dominant. So essentially the functions of, say, an INTP would be: Ti-Fe, Ne-Si. This does not mean Fe is "secondary".
Jung did argue that the three remaining processes were opposite orientation. He did also, however, talk about intuitive and sensing, and thinking and feeling, being highly separated, which would preclude a Ti-Fe one-two scenario.