Azure B2C Sign Out, then Sign In does not challenge the user with a password prompt

I am using Azure AAD B2C to manage my users and auth flow. I am trying to create a user experience where the user can log in under a different account. The user should be able to Log Out of their account and then click Sign In and be able to provide a different username and password.

However, currently I sign out. I can confirm through F12 debugger that all cookies are cleared. Then I click sign in and it signs me back into my previous account without challenging me for a username and password.

I'm not sure what is happening or why. Here is my Sign In code.

public IActionResult SignIn([FromRoute] string scheme)
    {
        scheme ??= OpenIdConnectDefaults.AuthenticationScheme;
        var redirectUrl = Url.Content("~/");
        var properties = new AuthenticationProperties { RedirectUri = redirectUrl, AllowRefresh = true };
        properties.Items["policy"] = "B2C_1_SignUpIn";
        return Challenge(properties, scheme);
    }

Here is my Sign Out code.

public async Task<IActionResult> SignOutAsync([FromRoute] string scheme)
    {
        HttpContext.Session.Clear();
        if (HttpContext.Request.Cookies.Count > 0)
        {
            var test = HttpContext.Request.Cookies.ToList();
            var siteCookies = HttpContext.Request.Cookies.Where(c => c.Key.Contains(".AspNetCore.") || c.Key.Contains("Microsoft.Authentication"));
            foreach (var cookie in siteCookies)
            {
                Response.Cookies.Delete(cookie.Key);
            }
        }

        await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
        await HttpContext.SignOutAsync(OpenIdConnectDefaults.AuthenticationScheme);

        return Redirect("~/");
    }

My Startup.cs looks like this.

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDistributedMemoryCache();
        services.AddMicrosoftIdentityWebAppAuthentication(
            Configuration, 
            "AzureAdB2C", 
            OpenIdConnectDefaults.AuthenticationScheme, 
            CookieAuthenticationDefaults.AuthenticationScheme);

        services.AddMvc();
        services.AddSession();  
        services.AddRazorPages();
        services.AddControllersWithViews();

        services.Configure<OpenIdConnectOptions>(Configuration.GetSection("AzureAdB2C"));
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseMigrationsEndPoint();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
            app.UseHsts();
        }

        

        app.UseSession();
        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthentication().UseCookiePolicy();
        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
                //endpoints.MapAreaControllerRoute(  
                //                  name: "Identity",  
                //                  areaName: "Identity",  
                //                  pattern: "Identity/{controller=Home}/{action=Index}");  
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}");
            endpoints.MapRazorPages();
        });
    }
}

My UI references the User.Identity.IsAuthenicated to determine if user information is present. Any help why it is behaving this way by automatically signing me in after I have signed out would be very helpful. I am new to OIDC and Azure B2C but I feel like I'm missing something very basic. Thanks in advance.