I wonder if what we think are 3D reliefs prepared from Volckringer patterns are not something altogether different. I suspect what appears to be 3D-ish elevation is a representation of relative chemical reaction completely unassociated with spatial relationships.
The veins appear higher than the blade and higher still nearer to the center rib. That would seem to be where the most lactic acid would be transferred to the paper by contact and lakes of vapor. The leaf seems really fat with an unnaturally beveled edge. That apparent bevel may result from less lactic acid reaching the paper at the edge of the leaf.
To fully assess this we need to see the facing pages from the book that held the leaf. Ideally, we need to see the leaf. We need to know which side of the leaf is being plotted for 3D content. I imagine the facing page’s imprint might have a similar appearance of elevated veins and a fat bevel. That would not make sense.
The point is that because something appears to have 3D characteristics, it may not be a real spatial representation. I’m not saying the Shroud’s image isn’t spatial data, what you call a height-field. I’m saying, however, that we must consider other possibilities.