That selective focus / depth of field argument only applies if you yank a lens from your 35mm body and use that same one on your APS-C or APS-H DSLR.
Given the same constraints (ie: distance from the subject), you will either use a different focal length to get the same image size on the sensor (thus cancelling out the DoF effect) or keep the lens and increase your camera to subject distance (to get the same target image size) and increase the DoF.
Remember, DoF is irrespective of focal length, it is a function of distance, f/stop and hyperfocal distance. What changes with varying focal lengths is field of view, and since field of view is inherently smaller in the typical DSLR this has the effect of making shorter lenses seem like longer ones.
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