No. Assuming the clamp attaches to the rails at the same spot, then having the clamp in in front of the post puts it about 2" forward of where it would be if the clamp is behind the post. The length of the rails on your typical saddle allow for about 1 1/2" of adjustment.
Ok, looking back at the pictures, I understand what you're talking about.
Was about to write a big ol' paragraph about not understanding the structural argument still, but then it all clicked. I wasthinking it'd put you further behind the clamp than the modern way, then realized that would probably put you right over the seat tube, which is exactly what doohickie was talking about (i think).