There is some ethical difficulty in running a study (and performing an intervention) on subjects who don't even know that they are in a study. In the application for a research position, people thought they were applying for a position, not tested for their responses to stimuli about the use of their work.

Obviously, certain kinds of results are impossible to obtain when you tell the subjects that they are part of an experiment. The value of the results might justify the deception, particularly in cases like these two studies in which the participants did not suffer any significant harm. But it is unrealistic to pretend that no deception occurred, or that deception is not a flag for potential ethical difficulty.