Why RequestTimeout WriteTimeoutResponse has never been executed

[code-jar]

Refer to this code

using Microsoft.AspNetCore.Http.Timeouts;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddRequestTimeouts(options =>
{
    options.DefaultPolicy = new RequestTimeoutPolicy()
    {
        Timeout = TimeSpan.FromSeconds(1),
        WriteTimeoutResponse = context => context.Response.WriteAsync("timeout")
    };
    options.AddPolicy("timeout-2s", TimeSpan.FromSeconds(2));
});
var app = builder.Build();
app.UseRequestTimeouts();
app.Map("/", () => "Hello world");
app.MapGet("/timeout", async (CancellationToken token) =>
{
    await Task.Delay(TimeSpan.FromSeconds(5), token);
    return Results.Content("No timeout!", "text/plain");
});
app.MapGet("/timeout-policy", async () =>
{
    await Task.Delay(TimeSpan.FromSeconds(5));
    return Results.Content("No timeout!", "text/plain");
}).WithRequestTimeout("timeout-2s");
app.MapGet("/timeout-catch", [RequestTimeout(1000)] async (CancellationToken token) =>
{
    try
    {
        await Task.Delay(TimeSpan.FromSeconds(5), token);
    } 
    catch (TaskCanceledException)
    {
        return Results.Content("Timeout!", "text/plain");
    }
    return Results.Content("No timeout!", "text/plain");
});
app.Run();

PS: You could that writes the response on timeout should check if the response has already started before doing so.

Originally posted by @davidfowl in #50607 (comment)

[davidfowl]

Did that comment not explain it?