Cutting this open uncovered a couple significant (Green Bastard) issues.
The replacement 1/4 was only welded to the rocker at the front and rear edges. The seam at the roccker was essentially loose. The inside of the panel was then filled with an entire caulking tube (or two) of silicone type sealant. This plugged the drain holes into the rocker, trapping water and rusting through both the lower edge of the inside door panel and the top of the ROCKER
There is enough left that this could be covered over but that's not me !!
So.... A piece of rocker will have to be repaired and an inner panel will be required.