Unnecessary defensive copies on enums passed by `in`

The compiler emits unnecessary defensive copies on enums passed by in.

Version Used:

Sharplab.io Also reproduces with the compiler included in the .NET 8.0.100 SDK

Steps to Reproduce:

using System;
public class C
{
    public void M<T1, T2>(in Enum1 value1, ref Enum1 value2, Enum1 value3, in T1 value4, in T2 value5) where T1 : Enum where T2 : struct, Enum
    {
        value1.ToString(); //defensive copy (unnecessary)
        value2.ToString(); //no defensive copy
        value3.ToString(); //no defensive copy
        value4.ToString(); //defensive copy (unnecessary)
        value5.ToString(); //defensive copy (unnecessary)
    }
}
public enum Enum1
{
}

Link

Expected Behavior:

None of the calls to .ToString() emit a defensive copy, since none is required for any of them.

Actual Behavior:

value1.ToString() emits a defensive copy, and similar for value4 and value5.