TextureCube sampling

No.

A long time ago, it used to be cheaper to sample from a cubemap than to normalize a vector... so there was a potential optimization where you create a cube-map that contains normalized normals, and then to normalize a vector, you use it to fetch a value out of this cube map!
These days this would be a terrible idea... But yeah, cube-map lookups have always taken any vector and have normalized them internally as part of the lookup process.