Yes, they still are useless, at least for the -O3 and -O4 sections.

The compiler removing the loop is due to a bad test setup in which the function in the loop does nothing and compiler can figure that out and skip the whole calculation. In a real scenario the function in the loop would (presumably) actually do some work so it could not be elided. Also, note that the compiler does this for BOTH the Duff's device version and the non Duff's device version.

Also, I'm neither attacking nor defending Duff's device. I'm just saying that we can't draw any useful conclusions from this article because of poor methodology.