Just in case some else finds this like me. The best method is to plug your metallic input into roughness and then just generate it as roughness but save it into a metallic texture. Then reconnect back to where it should be. Simple and effective without any shading (and roughness generates much faster than diffuse).
Each quad face is always made of 2 triangles in 3D softwares. I guess the result you see has to do with the way Blender will triangulate each of the 4 faces it creates when it subdivides.
Here I use a grid as image texture to make it more understandable. On the left, the original object, on the right, subdivided once. Here is how Blender triangulates:
If I ...
Bake Wrangler can do batch baking. It is free.
It is a 2019 add-on, so not many people discovered it yet.
I tested it and it can also bake from objects to another object.
The batch bake is in :-
Editor type = Bake Node Editor (must download & enable this add-on first)
Top bar > Add > Bake Wrangler > Batch Bake
Download at : https://...
You can bake this. Give the texture mesh an emission material. Select the object, then the target object (SHIFT).
In an image editor create a new texture (square, left)
Add an image texture node to the material of the target object,
select your new texture. It does not have to be connected to
anything, but make sure it's active (clicked on)
In the render ...