Warning [CS8622] caused by NotNullWhenAttribute

Question

Is this a bug in the compiler, or am I missing something?

public delegate bool Lambda<TState>([NotNullWhen(true)] out TState? state);

class Foo
{
  void Bar()
  {
    var lambda = new Lambda<string>(
      (out string? state) =>
      {
        state = default;
        return false;
      }
    );
  }
}

The compiler gives the following warning Foo.cs(14, 7): [CS8622] Nullability of reference types in type of parameter 'state' of 'lambda expression' doesn't match the target delegate 'Lambda<string>' (possibly because of nullability attributes).

But when I remove [NotNullWhen(true)] warning disappears.

This behavior first appeared in .NET SDK 6.0.402, there was no such warning in .NET SDK 6.0.101.