You've got it right, Ken. Sorry I wasn't more clear.
What I meant (hopefully this is clearer, but I'm not so sure
...), was that when punching a hole in steel, basically you first make a thin wafer, then shear that thin wafer/plug. In flat stock, it's easy to use your punch (usually flat, not pointed) to make that flat wafer by punching all the way to the bottom on one side, then flipping the piece over and shearing that plug out. In this case, the slug is usually cooler than the surrounding stock due to being the part driven against the anvil as well as the act of punching will deform the stock causing it to dish up a little.
In thick/hammer stock, it's impractical to drive the punch all the way through from one side for a number of reasons. One of them is the deforming of the block that will happen when driving a punch in from only one side. So, (and here's the point I was trying to make
) you punch from alternating sides until you make a thin wafer slug/plug in the center of the stock and then finish the job by shearing that plug out of the center.
But as I read your original question again, this might not have been what you were asking... If not, sorry.