From my understanding, duals with supporting subtypes have a more supportive/comfortable relationship than other duals.
An INTj (intuitive subtype) and ESFj (Sensing subtype) will have a more supportive relationship than INTj (logical subtype) and ESFj (Sensing subtype).
The first pair both have irrational subtypes that support each other, while in the second pair one has a rational subtype while the other has an irrational subtype, which do not provide the same level of support as the first pair.
Taking the second pair above as an example, would subtypes between duals alter/change in order to make the dual relationship most supportive and comfortable?
So for example the second pair in the above example alters to become exactly like the first pair: INTj (logical subtype) and ESFj (Sensing subtype) transforming into INTj (intuitive subtype) and ESFj (Sensing subtype).