No warning/error Severity CS8602 Dereference of a possibly null reference for optional argument

Microsoft Visual Studio Enterprise 2019 Version 16.9.4 (.NET Core 3.1 and .NET 5)

Looks like some edge case is missed when checking possible null references of optional parameters. In the code below the value for data reference will be null by default.

Function like: static void BadUse([Optional] Data data) => Console.WriteLine($"Data: ${data.Count}");

Expected Behavior: Warning CS8602 Dereference of a possibly null reference.

Actual Behavior: No suggestion/warning/error and null reference exception thrown on execution.

Note that it works fine when you do add DefaultParameterValue(null) attribute like (we get warning/error): static void BadUse([Optional, DefaultParameterValue(null)] Data data) => Console.WriteLine($"Data: ${data.Count}");