Right but what you speak of is common thought now, back then it was done was considered the most effective manner of conducting research. It was not until the 1970's the the Tuskegee project ended, and that was by a single doctor new to the project objecting to it, and bringing it to public attention. The Stanford prison experiment, Project MKULTRA, Stateville Penitentiary Malaria Study, Oklahoma sonic boom tests, and many others all had various physical, social, psychological, and economic effects yet each experiment was conducted on those who volunteered.
So think of this in terms of the 1930's: eugenics is considered a science, testing humans is effective, and dozens of other things of why the ends justify the means (don't think this, but people saw the world in such a matter back then). If the experiment was based upon the exact same test, yet consent was given what would be different?