As you can see in my previus picture, the lightning on metallic set to 1 is still trash.
in my guide I posted in OP they have a world position before material offsets, where the heck did that go?
The plane picks up other shadows fine, it’s the self shadowing that is broken.
for example, if I put a block over it, it will pick up the blocks shadow perfectly and distort it with the waves in a reasonably nice way.