问为什么Azure API管理隐藏状态代码4**和5**的响应正文

EN

<when condition="@(context.Response.StatusCode == 404)">
    <return-response>
        <set-status code="404" reason="NotFound">
            <set-header name="Content-Type">
                <value>application/json</value>
            </set-header>
            <set-body>@{
                var response = context.Response.Body.As<JObject>();
                foreach (var key in new [] {"HTTP Error 404. The requested resource is not found."}) {
                response.Property (key).Remove ();
            }
            return response.ToString();
      }</set-body>
     </return-response>
</when>