Unexpected behavior of object life with WeakReference usage

Question

This is my code,the results and expected results. Why alive = true instead of false on second line?

Results:

weakRef.Target is alive = True, expected true because inst keep a hold on SomeClass.
weakRef.Target is alive = True, expected false, because there is no more ref on SomeClass.

Code:

public class SomeClass
{
    public void DoSomething() { }
}

public static class GcHelper
{
    public static void Collect()
    {
        // OK surely overkill but just to make sure. I will reduce it when everyting will be understood.
        GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced, true);
        GC.WaitForPendingFinalizers();

        GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced, true);
        GC.WaitForPendingFinalizers();
    }
}

[TestMethod]
public void TestLifeOfObject()
{
    Action callback;

    var inst = new SomeClass();
    var weakRef = new WeakReference<Action>(inst.DoSomething);

    GcHelper.Collect();
    Debug.WriteLine($"weakRef.Target is alive = {weakRef.TryGetTarget(out callback)}, expected true because inst keep a hold on SomeClass.");

    callback = null;
    inst = null;
    GcHelper.Collect();
    Debug.WriteLine($"weakRef.Target is alive = {weakRef.TryGetTarget(out callback)}, expected false, because there is no more ref on SomeClass.");
}