Well, actually, cars require multiple hits to get fully destroyed unless you use Specials. The Hard Stomp wasn't working properly. The vehicles will get a light rework, so I hope that in the next update, we will have resolved those bugs. XD
Viewing post in Step 'N Smush [Macro Playtest] comments
Yeah I think what I'm seeing is the hitbox (for want of a better term) is a tiny bit inconsistent at times. Sometimes the car gets smushed, sometimes it doesn't (when it's on the edge of a stomp/special attack). The kick strike seems to be the most problematic in that regard... The 103 number comes from testing what states are considered "cars crushed" and then trying to get all of them... game is still fun though!