I think hes talking about that if you have two pipes coming out of a spark core from different faces, then each pipe can be 100 blocks in size independent of the other.
its not really anything to do with faces of a spark core, but just that a single linked set of pipe blocks is limited to 100 blocks, and if you are careful you can avoid the pipes from each of the 6 sides from touching eachother so that you get 6 indepdedent 100 block pipes