[neonsunset]

There is nothing particularly unidiomatic here - there are multiple ways to approach vectorization in .NET. Such low-level C# flavour is by definition something most developers would never write (even though it has gotten way more convenient and easier to do).

CoreLib heavily leans on "byref arithmetics" over pointer arithmetics, because this allows you to avoid object pinning and may have marginally better codegen at callsites, but it is by no means a requirement.

The code is fine, and it's not dissimilar to how SearchValues internal text search algorithms are implemented. It could be improved by factoring out platform-specific shuffle calls into a helper method and have the core use only portable method calls, but for the sake of demonstrating the point in the article it's absolutely fine.