Jungian typology is a system of preferences for various cognitive processes that therefore tend to form a cluster of preferences and work together as they inhibit the activity of antagonistic cognitive processes.
Basically if E N T and P work together to define a personality then I S F and J are inhibited.
The lower the differentiation - between a favored process versus its inhibited antagonist - the more likely to swap when the default cluster doesn't work.
That's the nuts and bolts.
If the default order of preference is, for example, E>N>P>T, when it reaches stalemate the most likely sacrifice will be T as it is the least differentiated. T/F most likely to swap, E/I least likely.
Or to put it the other way round, Jungian personality model is a hierarchy of differentiations.
Demonstration, if for a specific ENTP, T is more differentiated than E, then the cluster TI is more probable than FE as I/E will swap more easily than T/F. So if, for another ENTP, E is more differentiated than T, the cluster FE is more probable than TI. Yet for both and any ENTP, the cluster TE is always the most probable, and FI the least (putting other processes aside from the equation).