I have come to a conclusion of my own that these 4-groups were significant before, but from a different approach route:
Each of these groups are "comfortable visitors" to a certain adjacent quadra.
As an example, none of the types from ESFp-INTj-INTp-ESFj are Deltas, but none of them have a PoLR in the Delta quadra. Hence, you could say that the "comfort quadra" of this group is Delta.
The group of comfortable inhabitants of Delta, as such, is extended by these types: ENFp, INFj, ISTp, ESTj and ESFp, INTj, INTp, ESFj
This extended group could be considered to be more relevant to real observed situations than the quadras themselves, because quadras attract people who are comfortable in them as much as they attract people who are native to them.
However, "extended comfort quadra" is at the same time a battleground between the types from the "visitors" and much less comfortable to the quadra's native types than the original quadra, due to supervision from the visitors.
In reality I would expect a dynamic along these lines to unfold:
- a group of native quadra members attracts each other
- visitors from adjacent quadras to which the quadra is comfortable get attracted as well
- the group is now less comfortable to the original members
- the original members find themselves needing to ward off the visitors to make it as good as "the old days"
- it's possible that the group will choose a side in the battle between opposing visitors and turn into an alliance of two adjacent quadras instead