I'm similarly disappointed with the clarification on Force Push vs a wall with Passage Attacks. If I don't pay the 3 mana the Push basically does nothing, not even Bashing. I always thought of the Bash damage as "consolation" damage for not pushing them all the way through the wall. Ahh well. Guess I'm just disappointed because I love push spells
This was a tough call. Here was our thoughts: If you do not pay the 3 mana to Push them through the wall with the Passage Attacks trait then the Push did not have enough power to force them through it.
Think about it this way: the creature is going to be kicking and screaming to resist being pushed through that wall of Fire! You need a little more "umph" to get him through it! If you don't pay the extra mana the creature is successful in fighting the spell (resisting the Push) and does not hit the wall nor goes though it.
Also, many walls with Passage Attacks are
soft. For example, a Wall of Poison Gas (coming soon!), or a Wall of Evil Spirits (nasty to Living! - also coming!). There really is no bashing here, even if they hit the outside edge of the wall.
The concept of the Slam is that it requires a certain amount of power and momentum to effectively slam the creature, and stopping short of a wall was not enough. If you bash them into a wall without moving them a full zone, then that's what you did (instead of a slam into the floor or another creature) and you just got your attack on them. I will concede that we could have ruled otherwise. It was generally thought that you need to pick them up hurl them a full zone, gaining momentum with the distance, in order to do a proper Slamming.