Does any one know why AddSingleton and TryAddSingleton/TryAddKeyedSingleton dont have same overloads?

[zarlo]

does any one know what there is not a TryAddX version of this overload with both Type params like

  public static IServiceCollection AddSingleton<TService, TImplementation>(
    this IServiceCollection services,
    Func<IServiceProvider, TImplementation> implementationFactory)
    where TService : class
    where TImplementation : class, TService

the only overloads it has with implementation factories are

  public static void TryAddSingleton(
    this IServiceCollection collection,
    Type service,
    Func<IServiceProvider, object> implementationFactory)

  public static void TryAddSingleton<TService>(
    this IServiceCollection services,
    Func<IServiceProvider, TService> implementationFactory)
    where TService : class