The Meaning of Life, the Universe, and Everything.
What version of SEUS are you using? Seems like the texture size option only affects the Overworld so I would consider this as a bug in SEUS. They most likely use seperate shaders for the overworld and nether and forgot to implement the texture size into the nether one is my guess.
Incredible work! These are some quality textures that I love using.
I was just wondering - will you add any mcpatcher / optifine support? Having overlays for grass and other blocks connecting together would be awesome. Optifine added new glowing textures that this pack would greatly benefit from, as shaders make scenes quite dark. Random textures would be incredible, however I am aware that making these textures takes an incredible amount of effort and time, but the result would be worth it.