ngx.on_abort not work when register in access phase

Ubuntu18
openresty/1.15.8.1

nginx.conf

http {
    tcp_nopush     on;
    keepalive_timeout  65;
    lua_socket_log_errors off;

    server {
        listen       28002 reuseport;
        charset utf-8;
        keepalive_disable none;
        keepalive_requests 100000;
        keepalive_timeout 3600s;
        lua_code_cache on;
        lua_check_client_abort on;

        location /test-on-abort {
            access_by_lua_block {
                local ok, err = ngx.on_abort(function()
                    print("in on_abort callback function")
                end)

                if ok then
                    print("register success")
                else
                    ngx.log(ngx.ERR, "register failed: ", err)
                end
            }

            content_by_lua_block {
                print("in content phase")
                ngx.sleep(5)
            }
        }
    }
}

I test by curl, such as curl -i "http://127.0.0.1:28002/test-on-abort" and wait for 2 seconds, then 'Ctrl+C'.

error.log

2020/09/17 15:33:29 [notice] 15860#15860: *1 [lua] access_by_lua(dev-nginx.conf:69):7: register success, client: 127.0.0.1, server: localhost, request: "GET /test-on-abort HTTP/1.1", host: "127.0.0.1:28002"
2020/09/17 15:33:29 [notice] 15860#15860: *1 [lua] content_by_lua(dev-nginx.conf:74):2: in content phase, client: 127.0.0.1, server: localhost, request: "GET /test-on-abort
HTTP/1.1", host: "127.0.0.1:28002"
2020/09/17 15:33:32 [info] 15860#15860: *1 client prematurely closed connection, client: 127.0.0.1, server: localhost, request: "GET /test-on-abort HTTP/1.1", host: "127.0.0.1:28002"

When I move 'ngx.on_abort' from access to content phase, it works well.

Reproduce the report with the supplied nginx.conf, lua_check_client_abort on, and the /test-on-abort access_by_lua_block/content_by_lua_block sequence. Start at the ngx.on_abort entry point and compare registration in the access and content phases; done means the callback behavior is consistent when the client closes during the request.