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
{ name: zoomArg },
                zoomArgs[1] | 0,
                zoomArgs[2] | 0,
                zoomArgs[3] | 0,
                zoomArgs[4] | 0,
              ];
            }
          } else {
            console.error(
              `PDFLinkService.setHash: "${zoomArg}" is not ` +
                "a valid zoom value."
            );
          }
        }
      }
      if (dest) {
        this.pdfViewer.scrollPageIntoView({
          pageNumber: pageNumber || this.page,
          destArray: dest,
          allowNegativeOffset: true,
        });
      } else if (pageNumber) {
        this.page = pageNumber; 
      }
      if ("pagemode" in params) {
        this.eventBus.dispatch("pagemode", {
          source: this,
          mode: params.pagemode,
        });
      }