I still do not get why you have to store both, tame or wild, or both, all 4 DPs, a 4-way match as you said. Or just going back to the original statement, why it makes sense to store both, "...then you basically have two DPs found instead of one".
I think it was misunderstood. Where did I mention that both DPs need to be stored?
I said that when a DP is found, then you basically have two DPs. In a single database entry, since they both have the same X, hence the same hash (if Y is not used to affect the hash of the DP entry).
It shouldn't even be possible to store both - DP database keys must be unique for mast search. So an insertion will fail when a collision is detected, or when the DP hash collides, or when some kangaroo type collides with itself (and dies if the landed point is the stored DP point, not its opposite).