And on that note, this is exactly why I've learned to appreciate that the Deff Rolla does not work against vehicles. The Battle Wagon is a large enough target as is, but you can still overwhelm an opponent with enough threats that it may be ignored long enough to do it's job. If it could steam-roll over over other vehicles, it will have just become the largest target in my army list.. and would never survive past turn two.That's exactly how I read it too! Some people refer to adepticon tourny rules, but others say those are biased. I can't find anyone to argue against your post. A few Ork tourny players I know mention that reading the rules that way makes the battlewagon the most dangerous unit in the game. And will simply destroy Land Raiders. I still read it exactlly as you posted, and will argue that side until GW says otherwise.
True anytime a Deffrolla comes in contact with a vehicle it will likely destroy it with D6 S10 but you could still roll two 1's, and most tanks would just drive away. It's part of the orkish mentality for crying outloud! And any Marine based army should know that side and rear armour of a Battlewagon isn't unstoppable.