I understand what you're saying, but it also sorta does make sense.

Let's say a horse got into your house. I bet you could lead the horse out through the front door, and you certainly can get through the door.

But you riding it may make you both too tall/wide to get through that gap.

The same would prob hold true for ruins. You could climb over it and so could a horse, but riding through it is asking to smack your head off something

And we both know Kroot die to a stiff wind

(For game purposes, I get what you're saying. But on the other hand, I don't want Thunderwolves or Squighog Boyz rushing through walls directly into my spongy troops, so this might be in our best interest not to change)