How do static abstract interface members (C# 11+) enable generic math and other 'static polymorphism' patterns?

Interfaces can now declare 'static abstract' members (like operators or factory methods) that IMPLEMENTING TYPES must provide as their own static members — this lets generic code constrained to such an interface call STATIC operations (like T.Zero, or the + operator) on the generic type parameter itself, something previously impossible since static members couldn't be part of a traditional interface contract.

public interface IShapeFactory<TSelf> where TSelf : IShapeFactory<TSelf> {
  static abstract TSelf CreateDefault();
}
public class Circle : IShapeFactory<Circle> {
  public static Circle CreateDefault() => new Circle { Radius = 1.0 };
  public double Radius { get; set; }
}
T CreateShape<T>() where T : IShapeFactory<T> => T.CreateDefault(); // calls the STATIC method generically