const req1 = new undici.Request('http://localhost', {
  headers: {
    'set-cookie': 'a=1'
  }
});
console.log([...req1.headers]);   // --> [ [ 'set-cookie', 'a=1' ] ]
const req2 = new undici.Request(req1, {
  headers: {}
});
console.log([...req2.headers]);    // --> []
console.log(req2.headers.getSetCookie());   // --> [ 'a=1' ]   - unexpected!