I work with SEO, CRO, UX and I can confirm that this style of writing - short sentences, tiny paragraphs - results in better outcomes: time on page is higher and bounce rate is lower.
The title of the article is "Writing Well". It is not "Writing that Reduces Bounce Rates." These are not the same thing and marketing copy is not something every writer should seek to emulate.
The thing is, "Well" in "Writing Well" needs to be defined, because everyone sees it differently.
For some, "Writing Well" is writing in a way that gives the reader a emotional reaction, like lots of fiction tends to aim for.
For others, "Writing Well" is deconstructing concepts so people can understand complex ideas easier, like what most of technical writing aims to do.
For yet others, "Writing Well" is writing in a way that visitors on a website stays for longer and reduces bounce rates, like content marketing tries to do.
Like many things in life, what you understand "well" to mean, changes how you need to do your writing. Sometimes you need to switch how you see "well", depending on your goals. There is no right or wrong answer what "well" actually means.
I wonder if those metrics are like that because this style of writing has the reader thinking that the author has something important to say and has to spend a long time figuring out what it is because the sentences have been cut to the bone.
I honestly don't know, but the metrics rise on average, sending a positive signal to Google, which yields us higher rankings in Google, which equals more visitors. It's a constant battle between competitors -- finding out what the visitors want to read -- and how they want to read it.