How do I reflect nullability of a type's property in C# 9 when Nullable Reference types are enabled? [duplicate]

I am iterating the reflected properties of a type. I want to know which have been defined as nullable, and which are not. I believe the usual approach is:

 Nullable.GetUnderlyingType(property.PropertyType) != null

I am using .NET 5.0 and opted into Nullable reference types. Unfortunately this always returns False for both string and string?, whereas I expected the latter to be 'True'.

Project File

<TargetFramework>net5.0</TargetFramework>
<Nullable>enable</Nullable>

Type

public record MyRecord
(
    string ANonNullableProperty,
    string? ANullableProperty
);

Nullable Test

foreach (var property in typeof(MyRecord).GetProperties())
{
    bool isNullable = Nullable.GetUnderlyingType(property.PropertyType) != null;
    Console.WriteLine($"Property {property.Name} null: {isNullable}");
}

Expected Output

Property ANonNullableProperty null: False
Property ANullableProperty null: True

Actual Output

Property ANonNullableProperty null: False
Property ANullableProperty null: False

Is this a subtle defect, or have I misunderstood something? Is there a workaround or another way?