The crucial bit:

The fix is applying a negative mipmap bias into the game when upscaling is enabled. Mipmaps are used to generate gradually decreasing resolution textures, often used as a way to scale textures the further away from the player's view they land. It's recommended to set a negative mipmap bias to "generate a better texture detail" with upscaling enabled, and that's advice coming from AMD direct.

Yes, this mod simply follows AMD's own recommendations for upscaling as listed on the FSR 2 GitHub page and applies that to Starfield. It's a strange one, to say the least, as Bethesda partnered with AMD for Starfield, so you'd think would have all these technical details wrapped up. Of course, we don't really know why this wasn't set at the game's launch.