why request which is been aborted on puppeteer still can be get by server?

page.on('request', req => {
  try {
    const whitelist = ['document', 'script', 'xhr', 'fetch'];
    requestUrl = req.url();
    if (!whitelist.includes(req.resourceType())) {
      return req.abort();
    }
    req.continue();
  } catch(err) {
    console.log(err);
  }
});
await page.goto(url , {waitUntil: 'networkidle0'});

I use puppeteer to filter unnecessary resource like css or media。 but my server can still get css request. Why?