If your are getting a closer shave with a less sharp blade, it is only because you are shaving with excessive pressure to compensate for the "dull" blade. As soon as the apex of the blade contacts the outer sheath of the hair, it begins to penetrate the sheath at that point. Then as the leading edge penetrates further, the wedge shape of the blade forces the two parts of the hair in opposite directions until the hair is severed.
There may be some truth to the claim that a dual edge blade like the old Schick dual injector blades or modern multi-blade cartridges might produce a closer shave as the first edge starts to lift the hair follicle and the second blade then may be able to penetrate further down the hair shaft, closer to the skin. However, this can create a problem for those subject to in-grown hairs, especially if shaving ATG.
There may be some truth to the claim that a dual edge blade like the old Schick dual injector blades or modern multi-blade cartridges might produce a closer shave as the first edge starts to lift the hair follicle and the second blade then may be able to penetrate further down the hair shaft, closer to the skin. However, this can create a problem for those subject to in-grown hairs, especially if shaving ATG.