The point that is up for debate is that against war machines, shooting attacks are distributed to the machine, itself. I don't really agree that this is what "distribute as shooting" means in this instance, but I don't know how to disprove it either.
In a team game the other day, my teammate charged a steamtank into the Cauldron of Blood. The DE player, being a devious DE player

reasoned that since impact hits are distributed as shooting, all of the ST's impacts were resolved against the Cauldron's toughness of 10. Needless to say it wasn't killed, even though 11 S6 impact hits were done to it. I'd love to avoid things like this in the future. I like chariots, and hate war machines (that aren't mine) so this is sure to come up again...