No, wait… so the access stairs are on the outside (facing away from China)?

No, but to be fair, there weren't many stairs out in the open air anyway. Access is mostly through defended and barred towers and gatehouses not open stairs. And those towers all open towards China.

And the defense turrets do face inwards toward China?

Well, sort-of-yes, they face both ways.

Why the hell would the Chinese design defenses like that?

Because a wall like this serves multiple purposes. It's not just a wall, it's also a highway, patrol route, tax-collection point, propaganda piece and military base. But much more importantly: The parts of the wall in those pictures are later restorations and there is basically zero evidence they looked like this a thousand years ago.

Now, some super basic realities when you're designing a wall like this:

• Towers are wider than walls. You want them to stick out to both sides of the wall for more room, and so you can shoot the people on the wall from more than one side. So they stick out to both sides by basic design.

• They would march whole armies over these walls, and drive carts and wagons over them. You REALLY want something of a guardrail if you're doing that, and unless you like the idea of not being able to see what's on your side, you need crenellations in your side of the guardrail too. And sometimes, you might want to shoot at people on your side, for example when the enemy gets through. So you end up with a "double" wall. This is pretty common in European castles too.

• You want to keep an eye on people trying dodge taxes, break laws and do lots of other things you don't like to your side of the wall too.

• The wall and the towers served as a military base. And as any soldier in the history of soldiering will tell you, being on a military base in the middle of nowhere fucking sucks, and sneaking out is a timeless international passtime.

I don't know whether they are or not, I'd imagine given how large it is and the variation in how old it is there might be older sections that protected one part of china from another during times when it was broken up and is "facing" the other way. The point is, it doesn't matter. The series of conclusions they leap to is nuts, even if the thing they're leaping off of is actually true

Maybe the Chinese engineers just really sucked at their jobs