This problem applies to all the documents that I have ever opened.

Configuration:
- Web browser and its version: Google Chrome 83.0.4103.61 , also Firefox 76.0.1
- Operating system and its version: Win 7 x64
- PDF.js version: 2.3.164 version of extension
- Is a browser extension: yes

Steps to reproduce the problem:
1. Select any "Spreads" mode of view. Or "No spreads", but wrapped scrolling mode - doesn't matter. 
2. Select "Page Fit" zoom mode. We should get several pages per screen
3. Try to scroll document by any of keys: Page Down, n, j, Space Bar

I expect to see the next group of pages (for example, if there are 5 pages on the screen, I expect to see the next 5 pages)

What went wrong? Scrolling goes one page at a time, so if I have 5 pages on the screen, nothing happens when I pressed Page Down 5 times . For the 6th time I finally see the next group of pages.

Just for example: Adobe Reader scrolls properly in two-page mode, 2 pages at once. 

P.S. Sorry for my English, I hope I correctly stated the essence of the problem
return (this.baseUrl || "") + anchor;
  }
  /**
   * @param {string} hash
   */
  setHash(hash) {
    if (!this.pdfDocument) {
      return;
    }
    let pageNumber, dest;
    if (hash.includes("=")) {
      const params = parseQueryString(hash);
      if ("search" in params) {
        this.eventBus.dispatch("findfromurlhash", {
          source: this,
          query: params.search.replace(/"/g, ""),
          phraseSearch: params.phrase === "true",
        });
      }
      
      if ("page" in params) {
        pageNumber = params.page | 0 || 1;
      }
      if ("zoom" in params) {
        
        const zoomArgs = params.zoom.split(","); 
        const zoomArg = zoomArgs[0];
        const zoomArgNumber = parseFloat(zoomArg);
        if (!zoomArg.includes("Fit")) {