Assuming your definition of IDE is limited to GUI applications, and assuming you speak for everyone. Since neither is true, developing code on the terminal on a remote server is very possible and even practical.
The author is the one who speaks for everyone. I would like to use Xcode or Atom/Visual Studio Code.
And... by definition when you work on a remote server you are not developing on the iPad!
No, he doesn't. He speaks of his own experiences.
In fact, he states as much very clearly in the introduction: "The Mac and the iPad can coexist in a market where customers believe one is superior to the other. I prefer working on the iPad; others like their Macs more. And that's fine[...]".
His experiences only work for a few people. For example, Node.js is one the top programming languages being used now, how do you develop with Node.js in the iPad Pro? Java? C/C++? Go?
A well set up Vim or Emacs is perfectly capable of writing Node.js, Java, C (side note - hilarious that you tried to use this as an example, given that C and C++ are probably written by a majority of developers in the console) and Go.
We can assume if it's working for them then network connectivity isn't an issue (which is isn't for most of us, most of the time).
Node.js is not a programming language. It's a framework. I currently develop Node.js for work, and I always SSH into a remote machine to run tests and do development work. Developing Javascript, C, Go, and Java over a ssh connection is doable, one of the best options in the case of C and Javascript.
The same way I'm not developing on my laptop either, since I use a remote build server?
It might for you. There are tons of professional programmers, many who run circles around you and me, that don't use IDEs, but Vim, Emacs and the like.
Not my favorite app but proves it's possible. also: https://itunes.apple.com/us/app/raskell/id783015132?mt=8
Again not great yet because no one has put in the work to make a great version yet but it's complete possible.