This somehow sparked my interest so I looked deeper. In my project, I’m creating normal maps from height maps like you, so the initial normal map looks purple. The blue channel is white. The SDK build converts the textures to DDS. If I open these, the blue channel is black and the image is flipped in the Y or vertical direction. That’s the only differences I can detect just by looking at them.
I still believe that the blue channel is irrelevant here. The Y flip is the big deal though as obviously the normal map won’t work at all without that. The subtle thing to look for is the direction of the normals in the sim. Are the raised parts raised and the sunken parts sunken or vice versa.
An interesting aside is that in Blender, my normal maps look reversed but in the sim look correct. I haven’t dug deeper into that since everything works, but there are some mysteries.