PDFJS: Get some unnecessary chunks with range request and make first page slow

Question

Configuration:

• Web browser and its version: Chrome 97.0.4692.99
• Operating system and its version: MacOS 10.15.5
• PDF.js version: 2.12.313
• Is a browser extension: no

1. I use the range request to render pdf
2. I get more chunks with this line of code await this.pdfManager.requestRange(ex.begin, ex.end);;
3. These chunks are unnecessary when rendering first page;
4. The program also seems to run fine when I comment this line of code, and I can get less chunks to make the first page faster;
5. So what does this part of the code do?
6. Is it possible not to execute it or not to use await?

// src/core/xref.js

async fetchAsync(ref, suppressEncryption) {
    try {
      return this.fetch(ref, suppressEncryption);
    } catch (ex) {
      if (!(ex instanceof MissingDataException)) {
        throw ex;
      }
      await this.pdfManager.requestRange(ex.begin, ex.end);
      return this.fetchAsync(ref, suppressEncryption);
    }
  }

I can get less chunks when I comment this line of code and the program also seems to run fine

If I do nothing，the range request in network like this