Why does CompileToDynamicAssembly need a 4.6.1 lib?

[JustinGrote]

Hello,

I am trying to leverage CompileToDynamicAssembly to consume F# in Powershell similar to Add-Type. It works great except I have to supply this as part of the FSC options:
"-I"; "C:/Program Files/dotnet/sdk/6.0.100-rc.2.21505.57/Microsoft/Microsoft.NET.Build.Extensions/net461/lib"

Otherwise I get this error:

Add-FSharpType: startup (1,1)-(1,1) typecheck error The type 'BigInteger' is required here and is unavailable. You must add a reference to assembly 'System.Runtime.Numerics, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

Powershell does provide a System.Runtime.Numerics that is 5.0.0.0, but if I specify that with -I it doesn't seem to resolve it in either Powershell 7.1 (.NET 5) or Powershell 7.2 preview (.NET 6)

It has the same publickeytoken

EDIT: Opened related issue as it works with -r
#12302