为什么nginx压缩所有上游响应？

Question

我正在运行the official nginx alpine 1.17.1 image。

nginx.config：

http {
    include /etc/nginx/mime.types;
    index index.html;

    server {
        root /opt/myapp/wwwroot;

        listen 80;

        # enable gzip compression for content 1KB and over
        gzip             on;
        gzip_comp_level  2;
        gzip_min_length  1000;

        # supposed to be the default but whether or not
        # I add this line, the response from the proxied request
        # still gets compressed
        gzip_proxied     off;

        gzip_types       text/plain application/x-javascript text/xml text/css application/xml application/json;

        location /api/ {
            # this only way to disable gzip is for me to uncomment the line below
            # gzip off;

            proxy_pass https://api.example.com/
        }
    }
}

假设nginx在http://localhost:3000上运行，并且上游服务器从https://api.example.com/foo返回未压缩的JSON内容，则对http://localhost:3000/api/foo的HTTP请求将返回nginx压缩的内容。

我希望nginx不会压缩响应，因为它已被代理到https://api.example.com。

配置错误还是我误解了gzip_proxied？