Another problem with “writing as tightness” is that it would prevent the writer from surprising the reader. This is because, if writers only included vital details, eventually readers would figure out that every detail is vital. This would let them anticipate things that were supposed to be surprises.
An example: Suppose that in the last ten pages of your novel, it turns out to be vital that the hero knows how to speak Russian. You must set this up earlier in the novel to avoid a deux ex machina, so on page 30 you mention that when he was in college, your hero took Russian language classes. Now your readers know that this will be vital later, because they know you only include vital details. Thus they anticipate the rabbit you were hoping to pull out of the hat later. In contrast, suppose you’re not a devotee of the “only vital stuff” theory. When you mention that your hero took Russian language classes, you also mention that he took a classes in English Lit, Music Appreciation, etc., and that when he was in college his favorite beer was Imperial Stout. Because you’ve hidden the essential in the inessential, the reader cannot anticipate your surprise.
One might respond, “But then all that other stuff is essential: It’s essential for surprising the reader.” Certainly. But that’s different from being essential to the plot. This is the whole point: Things that aren’t essential for the plot may be essential for other important elements of the novel. I could tell the same story actually writing on page 30, “By the way, reader, at the end the main conflict is resolved due to the fact that the hero knows Russian.” Yes, it would be the same plot, but it would be a very different novel. It certainly would be a different experience for the reader, who would be denied suspense or surprise.