That rule was softened, so there are a bunch of apps like Pyto, Pythonista, Python2IDE, Swift Playgrounds (doesn't quite count since it's by Apple) that let you run code on the device.

I get what you're saying, but if your most advanced development capabilities are a Python interpreter and Swift tutorial then that's a sign that something else is holding them back.

Vim is on the app store, so I'm not sure what's holding Emacs back https://apps.apple.com/us/app/vim/id492668168

To add to that there’s also scriptable for JS

Emacs really isn’t allowed for the same reason TeX isn’t, everything needs to run from one binary. The single binary requirement of the App Store is surprisingly limiting.

Not sure what you're referring to. It's absolutely standard for iOS apps to load dynamic libraries that are bundled along with them. Additionally, Emacs itself doesn't consist of more than one executable.