"Switching" seems like a strong reaction, but there's something to the feeling the author describes.
I use vim quite a lot, every day. I also use IntelliJ IDEA every day. And yes, there's a bit of mental switching I do, and every now and then I use vim navigation keys while in IDEA, but generally it works for me. Different tools for different jobs.
Then again, I have no trouble loading reasonably large documents in vim, so maybe I don't have mine quite as customized as the author.
BUT I relate to the feeling of not being quite sure that all of my customization are quite enough, of not using vim to its full potential. Or even 10% of its potential.