because you want people to pay more for the dewalt version so you using 80% similar pieces and change to dies and then bam new productThese are the 12" clamps without the reversing jaw so they are indeed closer than the larger versions but as to your assertion that they are "the exact same", that's easily disputed by looking at the pictures.
The mold for the ribs is clearly different in both the body and the handle, the static jaw of the dewalt is not removable (no fastner) while the Irwin clearly has a phillips screw showing, and the pads of the Irwin are completely smooth while the Dewalt has a horizontal and vertical notch for centering the jaw on corners and rounds stock.
Though I'm not disputing it is possible, I don't know why the manufacturer would go through all the trouble of making the two clamps completely different if they come from the same factory.