Normalization and UTF-16 are completely orthogonal. It doesn't matter in the slightest whether the filesystem stores the filename in UTF-16 or UTF-8, either way

Normalization and UTF-16 are completely orthogonal. It doesn't matter in the slightest whether the filesystem stores the filename in UTF-16 or UTF-8, either way it's still a sequence of Unicode scalar values, and that's what matters.