Starting with .NET 5 the JIT emits code to read constant SIMD vectors from the data section which gives nice machine code and some related advantages like the ones listed in #1761 (comment).
See also dotnet/runtime#44115 for more context on that issue.

But changing the usage of constant vectors to the "inline variant" will regress pre .NET 5 targets, thus it seems best to keep current code with static readonlys, and update to the inline variant once .NET Core 3.1 will go out of support on 3rd Dec 2022 (the purpose of this issue is to have a remainder for that task).