Short columns aren't (only) about overall reading speed, it's about comfort.
When you're done reading a line your eyes must move back to the start of the next line. With short lines you can still fully see the end of the previous line so it's easy to locate. It's a lot harder to do with long lines.
I don't understand this logic. If I was uncomfortable using the entire width of my monitor, I would have gotten a smaller monitor instead. I find moving my eyes less annoying than moving my fingers to scroll; I often don't even rest my hand on my mouse or keyboard when reading, because I can use my hands for other things at the same time, or even just rest them somewhere else.
My point isn't that everyone will agree with me, but that all of these experiences are subjective. The only actually objective signal that the UI developer has is the width of the screen, so that seems like what should be used. Some amount of margin isn't unreasonable, but asserting that my display is "too large to be comfortable" is dogma, not science.
This doesn't reflect my own lived experience.