AFAIK modern HTTP versions like HTTP/3 can request multiple files in a single network packet. So it is basically free to do "another request". As the data request goes out and the data comes in in packets with other "requests".
import { x } from '/a.js';
import { y } from '/b.js';
Does not take longer than this: import { x } from '/a.js';
Because the message to the server "Give me b.js" goes out in the same network packet as "Give me a.js" and the data of b.js comes back in the same packet(s) as the data of a.js.