I expect the content of my document to look the same everywhere.

I expect the app that I use to view my document to behave like other apps on the platform.

It is Google's choice to make, the article is arguing that they made a poor choice. They can still make the app very Google-y in looks and organization but make it much nicer for iOS users by following a few platform conventions.

There is a very wide variety of iOS apps that look completely different but feel similar due to following the guidelines. Google should be able to fit into that.