I've never seen this before, where a 4" soil pipe must have been factory
made.

This was fitted into a 1960/70s council house.

Sorry the photos are poor, too many cobwebs etc.

Vertical pipe on left with 4" emerging to right
http://i66.tinypic.com/2iv01u1.jpg

Shows another 2" pipe emerging and heading off in the same direction as
other horiz 4" pipe.
http://i66.tinypic.com/34t48bt.jpg