What is easier for one audience may be more difficult for another.
Consider the original quote:
> Let’s walk through how Rebecca, an expert in plain language, translates a text to be more readable. We'll use an excerpt from her translation of a ProPublica article by Amy Silverman in the following example.
and the plain version:
> Here is an example for how to make writing easier to read. Rebecca wrote this example. She is an expert in plain language. This quote is from a news article. Amy Silverman wrote it for ProPublica. Rebecca wrote it in plain language.
In the plain version, there are six separate statements for me to process and remember. In the non-plain version, only two. They convey all the same information, but the non-plain approach clusters relevant information. It's the difference between trying to remember the number 1945 (nineteen fourty-five) and 1-9-4-5 (one, nine, four, five). You can both process and remember the former better because the information is usefully clustered.
Furthermore, as a skilled reader, it's easier to filter the non-plain one down to what I care about: "Here is an example of a plain language expert rewriting a paragraph." I find the plain version more frustrating because each plain statement seems as important as any other. No syntax clues tell me if "Rebecca wrote this example" is something I can discard.
In closing, I think this is a great article even if I disagree with the premise that simple language is a best practice. I like the article because it makes me consider how I should change my writing based on the audience.