That was a good call!
Testing and checking out the code it appears that what was considered "southern" region of the world within the terrain plant generation is set too far south, often into the
southern seas, and at the area where player character practically never visits. Now as the wolf pipe appears only in the south it indeed was practically non-existent in the world
where player characters roam. This might have hampered appearance of the other rare southern flora too.
It's fixed now, and wolf pipes can be found, although they aren't still too common.
Fixed - persists in 3.85